Algae Turf Scrubbers – How To Remove Algae

Update 03/22/12 The system has been updated.

Go to this page and look at post 28:


In the past 6 months, there have been several basic changes to the core concept of the Algae Scrubber, and these changes resulted in many people experiencing better growth and more effective filtration.

By far the biggest change is that the size of the screen needed for a given system is no longer dictated by the volume of the tank or the bio-load, but is instead based on the amount of food you add to the system. This has resulted in much smaller screen requirements; in some cases, ridiculously small screens when compared to the previously guidelines.

The second is the optional lighting scenario using twice the light intensity and half the photoperiod, which can power through the initial dark algae growth stages some experience, and can also be helpful in battling tough tank algae.

Third covers the advent of LED Algae Scrubbers.

I went through and edited the previously posted “Basics”, mainly for the purpose of addressing the 3 above items. Many other sections were also affected, and I have incorporated as many hints, tips, and tricks as I could. Even if you have read through the previous “Basics” summary before, read this one again. And again.

Some of the pictures in this are based on the old sizing requirements, but are still good for examples of specific principles. For this reason, and the lack of pictures of smaller builds using the new requirements, I have kept many of the pictures the same.

Part 2? Yeah yeah…I incorporated a little more into this one, and I have a start on Part 2, but it needs revamping too!

This will likely be the last summary revision for this version of the Algae Scrubber. There is a new version being developed (not by me) and it is currently being kept under wraps as it is in the middle of the patent process (again, not by me) so I know very little about it, except that it will supposedly have vast improvements in many areas, and will not resemble any Algae Scrubber that anyone has ever seen (this frustratingly includes me). The principles are all the same, so this summary has value still. But just be aware that a lot of this information (that I’ve but so much time into assembling…grrr!) might just get thrown out the window. Tidbits of info? On the new version, you won’t have to cut a slot in a pipe, can remove and clean the screen without shutting off flow,

Anyways….the re-revamped Basics:

Algae Scrubber Basics Summary: February 2012

There are many options when it comes to building your own Algae Scrubber. Hopefully this series of posts will wrap up all the basic concepts as clearly and concisely as possible. It seems that many people look at this concept and think they can make some kind of major improvement, and post their idea. Then, a newbie can look at that and think that it makes great sense and mimic it, without understanding the pitfalls. I feel that it is important to understand the concept and purpose behind the basics, and why you should rarely deviate from them without fully understanding the basic concepts first.

Most of the issues people encounter with their DIY builds can be directly attributed to missing one or two of the basic principles. So consider this a “best practice” summary. That is, there are several ways to build an Algae Scrubber, but there is always a cheap and easy way, as well as the most effective and efficient way.

The Vertical Waterfall Algae Scrubber

99% of this summary is dedicated to the basic of designing and constructing a modern, vertical screen, waterfall-style Algae Scrubber, illuminated from both sides. This is simply because this design is currently by far the most efficient and effective type of Algae Scrubber design, and the only one that I recommend building. The occasional mention is made regarding considerations to make for building a single-sided Algae Scrubber, or for a horizontal/slanted Algae Scrubber. From here forward in this series of posts, horizontal or slanted Algae Scrubbers will be referred to as “non-vertical”.

The vertical waterfall style Algae Scrubber is very efficient for a couple of reasons. The design allows you to illuminate the algae from both sides and place the lights very close, which reduces the distance that light has to travel through water in order to reach the algae. The water flow over the screen is relatively thin and moves fast; this is important, because algae requires turbulent flow in order for nutrients to reach the cells on a microscopic level (Google “boundary layer”). Because of both of these factors, vertical Algae Scrubbers require less light and material than the older style non-vertical Algae Scrubbers for equivalent filtration capacity.

The Slot Pipe, Screen, and Fasteners

The principal component of the modern vertical waterfall Algae Scrubber is the slot pipe and plastic canvas screen. The screen is inserted into a section of horizontal PVC pipe which has a slot cut into it. The screen is typically held in place with a fastener through a cut-out section of the screen, like this:……… go to post #28 on the site above to the the rest… :)


Algae Scrubber Basics: The Summary

Algae Scrubber Build Basics Summary

There are many options when it comes to building your own scrubber. Hopefully this series of posts will wrap up all the basic concepts as clearly and concisely as possible. It seems that many people look at this concept and think they can make some kind of major improvement, and post their idea. Then, a newbie can look at that and think that it makes great sense and mimic it, without understanding the pitfalls. I feel that it is important to understand the concept and purpose behind the basics, and why you should rarely deviate from them without fully understanding the basic concepts first.

Most of the issues people encounter with their DIY builds can be directly attributed to missing one or two of the basic principles. So consider this a “best practice” summary. That is, there are several ways to build a scrubber, but there is always a cheap and easy way, as well as the most effective and efficient way.

The Vertical Waterfall Algae Scrubber

99% of this summary is dedicated to the basic of designing and constructing a modern, vertical screen, waterfall-style Algae Scrubber, illuminated from both sides. This is simply because this design is currently by far the most efficient and effective type of Algae Scrubber design, and the only one that I recommend building. Mention is made of what considerations to make for building a single-sided or horizontal scrubber.

The vertical waterfall style algae scrubber is very efficient for a couple of reasons. The design allows you to illuminate the algae from both sides and place the lights very close, which reduces the distance that light has to travel through water in order to reach the algae. The water flow over the screen is relatively thin and moves fast; this is important, because algae requires turbulent flow in order for nutrients to reach the cells on a microscopic level (this is referred to as the “boundary layer”). Because of both of these factors, vertical scrubbers require less light and material than the older style horizontal scrubbers for equivalent filtration capacity.

The Slot Pipe, Screen, and Fasteners

The principal component of the modern vertical waterfall Algae Scrubber is the slot pipe and plastic canvas screen. The screen is inserted into a section of horizontal PVC pipe which has a slot cut into it. The screen is typically held in place with a fastener through a cut-out section of the screen, like this:

algaur turf scrubber

algaur turf scrubber


Slot Pipe

The slot pipe itself should be Schedule 40 PVC at a minimum. Don’t use vent pipe, flexible hose, or thin-walled PVC. The reason is that cutting a slot in the tube weakens it enough that it can bow over time and cause the slot to change width. This is especially true for a wide, tall scrubber. Anything over 24″ should probably have 2 slots, with a small section in the center left uncut (maybe 1/4″) with some kind of means of support at the center. It may look fine at first, but with heavy growth, you start to see this:

algae turf scrubber

algae turf scrubber

I’m not saying that it won’t work, and I’m not critiquing the design pictured above. It just got me thinking that it can’t be good to have that pipe flexing that much. So this is a recommendation I am making for scrubbers with screens over 24″ wide. But check out that growth!!! That’s 6.5 pounds of algae (drained).

Pipe Diameter

When running a scrubber fed directly from the overflow, there is usually no need to deviate from the size of the drain pipe that you currently use. But, that all depends on your total resultant flow to the pipe, length of screen, etc. In the majority of cases, this doesn’t change anything. However, if you had a large tank, and were combining 4 1” drain lines together to feed one large scrubber, you have different considerations.

If you’re doing a pump fed scrubber, either top of tank or sump, try to match the size of the slot pipe and other PVC components to the recommendations from the pump manufacturer, and if in doubt, err on the side of larger pipe. Larger pipe puts less head pressure on the pump, which will increase the flow rate.

Cutting the Slot

The width of the slot should be approximately 1/8″ wide, the same length as the screen which you are using (as exact as possible), and as straight as possible. Cutting a straight, even width slot is arguably the most difficult part of building a scrubber. It is also one of the most important steps. If the slot is crooked, the screen may not hang properly, and there may be areas where the flow is lighter and heavier. This can result in sections of weak growth.

However you go about this, you might need a few tries to get good at it. PVC is cheap, so practice on a small section so you get used to how this is done. It’s going to take a little time and patience – don’t rush it. Mark the slot, and cut carefully. If you mess up, do it again. Once you solvent weld an end cap and a union to it, it is not as cheap to replace (but still relatively cheap).

Doing it right means using a power tool. Probably the most common tool for this use is a rotary tool, or a Dremel, using a cutoff wheel:

Slot Cut Off wheel

Slot Cut Off wheel

Another idea is to use a router. Since plastics are ‘grabby’, and plunge routing plastic takes extra grip and control, extra precautions apply – so this is not for the inexperienced, but it makes very straight slots. This method requires building a guide jig for the router, and a clamping system to keep the PVC firmly in place.

Reportedly, the best way to cut a perfectly slot straight is by using a table saw. However, there really is no way to cut a slot in the middle of a section of pipe (or across the whole length of the pipe) without removing the anti-kickback device and lowering the pipe on to the spinning blade. You could also do it with a handheld circular saw, but like the router method, you would need a jig and clamp system, and you still are lowering a spinning blade onto the PVC (if you’re cutting the slot in the middle and leaving the ends uncut). I have never tried this and I do not recommend this method because it sounds too dangerous.

However you decide to cut the slot in the pipe, remember to observe all necessary safety precautions. Either that, or have someone else do it for you.

Screening Material

The search for the “perfect material” for growing algae in the vertical waterfall configuration has always come back to the same material, the Clear #7 Mesh Plastic Canvas. This can be found at almost any fabric (Jo-Ann Fabric) or craft-type hobby store (Michaels), usually in the knitting materials section. I have seen it at Wal-Mart, next to all the yarn. If you google “plastic canvas” you’ll find hundreds of links. You can feel free to experiment, but this material has been proven to work over and over again.

The reason that it works so well is because it is cheap, flexible, light, and easy to rough up. It is also translucent, which is critical. As algae grow thicker on a screen, the outer layer starts to block light to the lower layers. This causes weakening of the algae at the point of adhesion to the screen material. Allowing light to penetrate to the base of the screen from both sides helps to prevent the lower layers from weakening and detaching from the screen. Any material that blocks light is fundamentally inferior, all other things being equal. This also means don’t use any of the colored screening materials that you will see.

A brand new screen is slick and smooth. Except for the top edge of the screen, it needs to be roughed up with a hole saw or a rasp so that the algae has anchoring points. This is a critical step and it absolutely must be done properly. Once the screen is established, algae can grow very thick, it can hold a significant amount of water, and it will get heavy. I have seen pictures of screens that weigh several pounds. This weight is distributed across the screen, and with a rough base, it will hold very well.

To rough the screen up, you want to use a bi-metal hole saw. These saws have teeth that protrude out to a sharp point, and are great for tearing up the screen

Hole Saw

Hole Saw

As the above picture shows, you need to drag is back and forth across the screen. I suggest you sit in the garage or outside with a cutting board on your lap and lay the canvas on that. When you start roughing the screen, do a lot of random movements. Don’t concentrate on one spot for very long or you’ll wear through the screen and tear it. Rotate the screen often. You can also tilt the saw bit as you drag it so that the teeth won’t snag the screen. You should get a good heaping tablespoon of plastic from each side of a 10×10 screen.

After it’s all done, your screen should look like this:

algae scrubber plastic Canvas

algae scrubber plastic Canvas

Give the screen a good rinse and a light scrub with an old toothbrush to clear off all the pieces that are ‘hanging by a string’. These pieces are inert plastic, but still, you don’t really want these floating around in your aquarium.

Though I haven’t used one myself, I have heard that a rasp (available at any hardware store) is also great for roughing up this material. There are handheld rasps (similar to a Ped-Egg for your feet, except much sharper), and there are bit-mounted rasps (for power drills). It looks like it could be a little easier to tear the screen with this tool, but there is much less elbow grease involved. The drill bit rasps I have seen don’t appear to have protrusions large enough to “dig” into the screen and result in a cactus-rough surface.

Some have tried other methods of roughing up the screen. 80 grit sandpaper will definitely rough up the screen, but it doesn’t leave it ‘prickly’, so it’s not very effective. Recently, someone put a screen in the oven for a few minutes, then sprinkled it with aragonite sand and pressed it on; this blocks the light from penetrating to the base from both sides, but it’s still a cool idea, so time will tell on that one.

The bottom line here is that there really is no shortcut. You only have to rough up the screen once, so stick to the tried and true method, unless you feel like experimenting on your aquarium.

As previously mentioned, the top edge of the screen (where it is inserted into the slot pipe) should not be roughed up at all, or else algae can easily grow into the slot and restrict the flow. The amount of material you leave smooth depends on your design, mainly, how far you plan on inserting the screen into the slot pipe. Regardless of this measurement, the smooth section should extend at least 1/8” down below the slot.

I repeated get questioned about the risk of the slot clogging with algae and overflowing your tank. Instead of addressing this concern here, this will be addressed in Part 2 (which I again promise to get done soon).


Most people use zip-ties to secure the screen to the slot pipe, since they are cheap and easy to use. Generally you have to use new ones each time you clean the screen (because you have to cut them), or you can re-use them if you’re handy with the tip of a razor blade and can get them to release.

You can also use releasable zip ties (I found them in the electrical section of Home Depot), but they’re not as easy to release as you would think they would be, unfortunately. I use them, and I still need a mini-screwdriver to take them off.

Velcro straps can also be used, however they need to be free of adhesives, and I have never been able to get an answer from manufacturers about the stuff that has hooks on one side and loops on the other (such as OneWrap) regarding their safeness in aquaria. “Medical Grade” would be the safe way to go, but I haven’t looked much into those.

The latest one brought to my attention is the nylon beaded cable tie, which, like the zip-tie, is inert, but super-easy to release, so it’s good for months and possibly years.

Beaded zip ties

Beaded zip ties

The only drawback I can see it that you can’t cinch them down super-tight, but this doesn’t matter unless you hold the screen in place at the center only with the screen inserted all the way into the tube. Most people hold the screen in with one tie at each end, and maybe one in the middle, so this is less of an issue.

Another method of holding the screen in place is to use plastic shower curtain rings. It works very well, however you should have extras on hand in case one breaks when you’re removing it.

Yet another is to use sections of PVC pipe, one size larger that the slot tube, to make rotatable rings. This works very well, just make them narrow so that they don’t block too much flow.

I’ve seen a few designs that don’t use fasteners, but there are considerations to make with these designs. I decided to discuss these issues in Part 2.

Preventing water creep along the pipe

This is an important part of the slot pipe design. The issue here is that when you are running water though a horizontal pipe with a slot in the bottom of it, the water has a tendency to creep along the bottom edge of the pipe, not matter how perfectly horizontal you install it. If your scrubber is positioned completely over your sump, this may not be a big issue, as any errant flow will just drip into the sump. If your pipe ends extend close to the edge of the sump however, a steady trickle of water can result in gallons of water on the floor. I can attest to this.

The solution is very simple. Right at the point where the slot ends, place a large plumbing gasket, such as an o-ring (use several, they’re cheap), or even a bulkhead gasket. The point is that it needs to prevent water from getting past it. I can tell you from experience that a standard zip-tie will not work – the profile is too low.

In many cases, you need to put this piece on the pipe before you weld the cap on the end of the pipe, or else it will be very difficult to install. This one is a ballcock washer, and definitely needs to be installed before the cap is installed:

ball cock washer

ball cock washer

Planning your Scrubber

There are 2 basic ways of supplying flow to a scrubber: directly from the overflow, or from a dedicated pump.

Types of Algae scrubbers

Types of Algae scrubbers

The above diagram does not illustrate the top-of-tank scrubber, which would apply to someone running a sumpless system, however this is just a modification of the pump-driven scrubber with the pump in the display tank.

The very first step you need to do before buying, measuring, or sketching up anything, is to decide how you are going to supply your scrubber, and determine what your available flow rate is.

Available Flow

In any case, you need to measure the flow rate. Do this step. It is critical. Do not, I repeat, do not calculate the flow rate based on pump curves and head-feet of pressure. This may sound like a total pain in the behind, but just trust me on this one. Would you rather go through all the effort of building a scrubber, only to have problems and find out that you didn’t have as much flow as you thought you did? Believe me, I’ve been there.

If you’ve been reading this thread, you will see that at some point I started making a big deal about this. The reason is that it is a big deal and I think many people don’t realize that their pump does not pump at the rated flow, and in the majority of cases, it doesn’t come close to the flow calculated by using a standard head-foot calculator program or table. So I have chosen to make it the #1 priority for scrubber design, hands down. You have to know your actual flow.

For a drain fed scrubber, fill a pitcher with the water entering the sump. You will probably need to rig up a temporary pipe or routing configuration so that you can fill the container. For a pump-fed scrubber, set up the pump in a sink filled with water to the same level as your pump will be submerged, and connect the tubing required to reach the height of the connection to the horizontal slot tube, so that you mimic as best as possible the actual conditions. Backpressure created by the slot/screen is negligible unless your flow rate significantly exceeds 35 GPH per inch of slot length.

Now that you’ve done all this, fill the container and record the time it takes to fill it. Do this at least a dozen times. The way I do this is by using a recording device, like a digital voice recorder, and just calling out “Go” and “Stop”, then afterward, playing it back and using a stopwatch to get the time intervals. You could also have someone else run the stopwatch and write down the times. Average out the times and then figure out how many gallons per hour of flow you are actually getting. If you have multiple drains, measure and extrapolate GPH for each individually, and then add together.

For instance, if you are using a 1/2 gallon pitcher, and it takes 4.5 seconds to fill it, then you would have (0.5 gallons / 4.5 seconds) x (3600 seconds / 1 hour) which would be 400 GPH.

Don’t be surprised if you have a lot less flow from your pump than you thought you had. I had less than 1/2 of what I thought it was. Head-feet calculations are usually way off, because most people don’t use big enough return hose or have other restrictions in the plumbing. Some of it is inherent to reef-ready aquarium design (1″ drain, 3/4″ return, Danner Mag-Drive 9.5 and larger pumps need 1.5″ return, see a problem?). So don’t feel bad. A lot of people are in your situation, but they just don’t know it.

Start with a clean pump. If your pump is not clean, soak it in vinegar for 15 minutes and scrub it good. After running a scrubber for about 4-5 months, your pump flow will drop about 15%, and by 6 months, it will have dropped by 25%, so you want to know your best-case flow and build around that. It’s a lot easier to start with a throttled-back clean pump and open it a little when the flow rate decreases. Figure out your system flow rate, multiply by 80%, and that will be a good starting point. But, it’s not going to kill you to start at full flow, and end up with a little less over time. You might just want to clean your pump a little more often, say every 3 months. So it’s up to you. Just being aware of your system conditions puts you miles ahead.

Screen Size

Once you figure out your available flow, then it’s time to figure out your optimal screen dimensions.

There are 2 ways of looking at this: square inches based on length and width dimension, and square inches based on illuminated surface area. The latter is technically more accurate, but since most people light both sides, the former is usually referenced.

For every gallon of water in your display tank, you need 2 total square inches of illuminated screen material. This means that if you run a screen that is vertical and lit from both sides, then you need a screen with dimensions (length times width) that is equal to the size of your tank, or 1 square inch of material per gallon. This is what you will see commonly referenced, and what I continue to reference for simplicity’s sake. Double the dimensional measurement for a vertical screen, lit from only one side. Double it again for a horizontal or slanted screen.

Sizing of the screen generally does not require inclusion of the volume of water in the sump, unless you have some kind of bio-load in there, like a refugium for a recovering fish, pods, or a frag tank, etc.

So, just so we’re 100% clear on this:

Vertical, lit from both sides: 1 square inch of screen material per gallon (2 square inches of illuminated screen area per gallon)

Vertical, lit from only one side: 2 square inches of screen material per gallon (which is also 2 square inches of illuminated screen area per gallon)

Horizontal: 4 square inches of screen material per gallon (4 square inches of illuminated screen material per gallon). Lighting must increase by a factor of 1.5 (discussed in the lighting section). Also note that this is a correction to what was listed on Post #1 of this thread (that post listed that a 10 x 10 screen was good for 40 gallons, instead of 25 gallons)

Screen Dimensions

So now that you know your actual flow rate AND the total size of your screen (and you need to know the total dimensional area for this part, not the total surface area), now you are ready to figure out your dimensions.

You want the flow to be as close to 35 GPH per inch of screen width as possible. You can get by with a lower flow rate, but your scrubber may not be strong enough depending on your bio-load. You can have higher flow also, which is generally not a problem as long as your screen is rough enough and you aren’t getting black slime algae (which is a sign of high nutrients, and needs more frequent cleaning until it lightens up. What you want to achieve is enough flow so that you have a full sheet of water across the screen off the bottom edge, like this:


water flow rate over algae scrubber

water flow rate over algae scrubber

Simply take your GPH (that you just measured) and divide by 35, and this will be your optimal screen width. Then, take that number and divide it into the gallon size of your display tank to obtain the height dimension of the screen. Use the size of your tank, not the gallons that you think are actually in it (so do not account for volume of Live Rock, fish, decor, etc) and do not include your sump volume (unless there is significant bio-load, as previously described). The result is the total area of roughed-up screen that you want.

In general, you want to add at least one inch to the height dimension for the section of smooth screen that will be inserted into the slot pipe. Specifically, you want to allow for the distance that the screen will be inserted into the slot pipe, plus at least 1/8″ of smooth screen below the slot tube to help prevent algae growth into the slot. This “one inch” is just a good rule of thumb, and should be increased depending on the diameter of your slot pipe and how far you insert the screen into the slot pipe. A little extra smooth screen at the top never hurts, as it can be trimmed off later.

The critical area, and the only area that contributes to scrubbing power, is the roughed-up and illuminated portion of the screen. Figure out your necessary screen dimensions, then add the extra smooth section to the height dimension.


There are 2 basic types of light sources that 99% of people use: CFL and T5HO. In both cases, the optimum spectrum / light temp for growing algae is 2700K-3500K, with 2700K-3000K getting the best results.

Proper wattage of light and proper flow to the screen are the critical factors; color temperature / spectrum comes in behind those. You can use higher K ratings, but the real-world (anecdotal) evidence suggests that the optimal range for growing algae is heavy in the red spectrum. If you look at regular plant grow lights, you will find that most of them (especially LED grow lights) are very heavy in red.

Power Compact, or PC lamps, are not recommended, because they run way too hot for the amount of light you get out of them. I don’t even care for them for tank lighting.

I have slightly expanded the discussion regarding LEDs. This is still a relatively unproved area, but as more people build LED scrubbers, more information is being confirmed. There are still plenty of unanswered questions, so LED scrubbers are really more of an advanced subject.

Quantity of lighting is dependent on the size of the system. In general, you want 1 watt (actual, NOT “incandescent equivalent”) of light per gallon for optimal scrubbing power. You can get away with less, but at the worst case you should use no less than 0.5 watts per gallon.

When I say “watt per gallon” here, I am referring to the size of the display tank, which is what is used to calculate the size of the screen. For the majority of people, the size of the screen matches the display tank size. If you decide to under or oversize the screen, you would then match the wattage required to the screen size. So if you have a 100 gallon tank, but you build your screen like it was on a 150 gallon tank, then you would want 150 watts of lighting.

As you will notice throughout this thread, it is generally stressed to follow the 1 watt per gallon guideline. This is because it solves many scrubber issues. The reason behind this is scientific. Light interacts with algae and causes N and P (and ammonia & nitrite, among other things) to be absorbed, and chlorophyll is created (among other things). The more light, the more nutrient reduction you get. There is a direct correlation between the quantity of light supplied and the amount of nutrient reduction capability.

A horizontal or slanted scrubber requires 1.5 watts per gallon, without exception. This is mainly because the horizontal scrubber has a much larger surface area to cover, so you need more light sources to spread the light out evenly. Also, horizontal/slanted scrubbers are generally not as efficient, unless you use a dump-bucket or surging style, which are more complicated.

You need to run your lighting for 18 hours on, 6 hours off. All life needs downtime. Plants are no exception. They have adapted to the environment over millions of years, and as the saying goes, you can’t fool Mother Nature. So don’t go thinking that you can run lights 24/7 and get 25% more algae growth, it doesn’t work that way. The lights should be run on the reverse cycle of your display tank lighting; this assists in maintaining pH at night, as well as spreads the light-induced heat load more evenly throughout the day.

You want the lights as close as possible, within reason. The effective power/intensity of light follows the inverse square law. If you move a light twice as far away, the intensity drops by a factor of 4. If you move it twice as close, you get 4x the intensity. The balance point seems to be about 4″ from the screen for CFL, and about 2″ with T5HO. The reason for 4″ away for CFL stems from hot spot issues due to the concentrated signature of the lamp; CFLs need to be a bit further away to cover the proper area without too much intensity. T5HOs do not have this problem, as the light is very evenly spread.

As far as spacing is concerned, CFLs need to be spaced according to the allowance of the design. If you need 2 per side, just position them for the best coverage. This is really on a case-by-case basis. As for T5HO, you generally want a lamp spacing of 2-3″. For T5HO, your scrubber will generally need to be designed around the lamps and spacing. CFLs are more flexible in this respect, allowing a variety of configurations.

The lamps must be replaced every 3 months. This is not just a rule for scrubbers, you will see many people make this suggestion for refugium lighting as well. That is because there is a power drop-off and a spectrum shift that takes place over time, and when you go much past 3 months, you hit that drop-off point. We can’t see the difference, but then again, we’re not algae – it can. The result is that your screen will slow down growing and reduce filtration, which you do not want.

The light source needs to be positioned so that it is pointing directly at the screen material. Do not place the fixture so that it points parallel to the screen (from the ends or the top), place it so that directs the light toward the screen. Perfectly perpendicular is optimal, but if you have to point it at somewhat of an angle just to make it work, that will be fine. This is more of a concern for CFL than linear sources (T5HO), however I have seen a few T5HO build with the lamp 4 inches above the screen, shining straight down. They didn’t work so well.

CFLs and Reflectors

The most common CFL used is the 23W Spiral. This is the actual wattage, not the equivalent wattage. There are a few different type of CFL lamps, and each one has a different ideal application. These are: spiral CFL, linear CFL, floodlight CFL.

A bare lamp will work without a reflector, but it will do the job much better with one.

Spiral CFL

CFL light bulbs

CFL light bulbs

The spiral CFL is definitely the most common type available and the most widely used. There are 2 ways to orient the lamp: with the end pointing at the screen or with the side facing the screen.

With the end lamp pointing at the screen, a reflector is a must-have piece of equipment. Without a reflector, a lamp pointed directly at the screen will do very little, since a small percentage of the light comes out of the end of the lamp. The cheapest, easiest, and most common reflector for this orientation is the dome-style reflector, which is available just about anywhere.

This reflector provides a wide light signature, since the side light is reflected to the front. They come in several sizes, and you want the biggest reflector you can fit in the space.

The dome reflector does the job just fine, and one of these should be used at a minimum. However, it is by no means the ‘perfect’ reflector. The reflector has a ribbed, dull surface that does a good job of diffusing the light, but it is not as efficient as a shiny, highly polished spectral reflector. Also, about 1/4 or so of the lamp (depending on the brand) sticks out past the reflector, and most of that light does not get directed toward the screen.

With the side of the lamp facing the screen, the reflector is usually a DIY job With a side-style orientation, more light is shed directly to the screen, but you still need to re-direct the light from the sides and back of the lamp towards the screen. There are a few fixtures that you can buy with integral reflectors, but most are very small. Most off-the-shelf light fixtures are for use in a shop or garage and have a half-round solid section, which may or may not have a reflector. If it does not, you can simply line it with aluminum foil or another highly reflective material.

The setup below uses off-the-shelf shop lights. The fixture on the left has reflective material installed.

Shop light algae scrubber

Shop light algae scrubber

The advantage to the side-lamp design is that since you can hang the lights from above, they generally take up less space (depending on your reflector) versus the dome reflectors.

In order to spread the light out evenly and wide (but not too wide or you’ll lose intensity at the screen), you want a wide reflector. Finding such a reflector is not easy. Since spiral CFLs can be considered a point source (more of a “blob” source, but this is for simplicity), using an HID reflector can be effective. A DIY beer can reflector can work also. Even some Mylar or aluminum foil will do the job.

Searching for a flexible reflector material and making your own reflector will yield the best results. A properly made reflector for a side-lamp orientation, such as the one shown below, can direct almost 100% of the light toward the screen.

custom cfl light reflector

custom cfl light reflector

Linear CFL

Linear CFL lamps are commonly referred to as twin, triple, or quad tube, etc. They are similar in nature to Power Compacts in that the lamp is in a “U” shape, but commonly have an integrated ballast like a CFL. They are usually higher wattage than standard CFLs, are more intense, and can run hotter. However, since they use the screw-in base just like CFLs, they are easy to use and I have recently looked at a couple of nice builds using them, so I thought it was worth adding a section covering them.

Linear CFLs would be installed similar to the sideways spiral CFL, hanging the lamp from above. Reflectors are generally the same principle; however the source is now more linear, so your reflector in turn should follow the line of the lamp and curve around it. Here are a few of the better ideas for this that I’ve seen. One uses cut-up linear fluorescent reflectors, the other uses mirrored acrylic.

A reflector similar to the last one in the spiral CFL section could be done. Because the lamp profile is more linear, the reflector would be slightly different dimensions – probably more square than rectangular.

Floodlight CFL

The floodlight CFL is simply a spiral CFL enclosed in a lamp housing like you would see for a standard incandescent floodlight. They are not very efficient at spreading light when placed in close proximity to the screen, as the light is diffused at the end of the ‘bulb’ and the reflector is of a small diameter. However, they are good for use on smaller, narrower screens – ones that have one dimension less than 6 inches. They should generally not be used for primary lighting, unless you are running a small scrubber, like for a 20-35 gallon tank

You can see in this picture that the floodlight only provides significant light to the area directly in front of the lamp – and that’s the only place that’s going to provide adequate filtration:

They can also be helpful to supplement light from dome-reflector setups that just need a little more light but there’s not enough space for another dome.

One thing to remember when handling CFLs: install them gently. Most people are used to twisting in an incandescent lamp tightly. CFLs fracture easily at the base where the element (tube) meets up with the ballast. Cranking on them like causes these fractures. So if you can’t grab on to the base to tighten, just get the lamp in there snug enough for the connection to be made. This goes for the lights in your house and office also – it’s the #1 reason why CFLs burn out early.

T5HO lamps and Reflectors

T5HO lamps are inherently superior to CFLs. They spread the light out more evenly than CFLs, and they can be placed closer to the screen without overpowering the algae. Notice in this picture below how use of T5HO can result in almost perfectly even light coverage:

t5 ho light for algae scrubber

t5 ho light for algae scrubber

With that factor alone, bare T5HO lamps likely fall in between bare CFL and properly reflected CFL as far as scrubbing power is concerned.

Reflected T5HO is very arguably superior to all. However, it is more difficult to build a T5HO scrubber. You either need to buy and build around a stock fixture, like the Nova Extreme 1126/1127, or build something upon which to mount and protect endcaps, then connect to a ballast. Also, since the reflectors are generally one of the more expensive components, enclosing the screen in an acrylic or glass box is pretty much a given. However, in my opinion, it is worth every penny.

As far as lamps go, the same rules apply. I personally use the PlantMax 3000K Red/Bloom lamp, I can get them for $4 in packs of 8, which is about the cheapest I’ve been able to find for good quality lamps. Here’s my scrubber, Revision #2 (Rev 3 coming soon)

With a custom build, you can really use all the power of a T5HO lamp. The TEK-II reflectors from Sunlight Supply are expensive, but I have had great results. Other individual-lamp reflectors, such as Ice Caps, work very well. Stock fixtures work best when each light has an individual reflector, but just about any reflector will do better than none.

Sunlight Supply also makes a T5HO fixture that needs no external ballast, and you can daisy-chain up to 10 of them together. However, the reflector they make for it is just plain aluminum and nowhere near as reflective as the TEK-IIs or Ice Caps, which use Anolux-MIRO IV (which is something like 96% reflective)

The disadvantage to T5HO is that you’re pretty much locked into a dimension that you have to build around. T5HO lamps come in standard lengths of 24”, 36”, 48”, and 72”. There are shorter lamps, such as 18”, but it’s difficult to find lamps in the right color temperature, and they’re generally much more expensive than 24” or 48” lamps (which are the cheapest T5HO sizes). This means that the dimensions of your scrubber are locked into about 20-22” in length, which is the illuminated length of the lamp (the fixture is 24”, the lamp right around 21” long). This means your flow to the screen has to be around 700-800 GPH. You can make the screen narrower, but you will end up wasting part of the lamp. The benefits of T5HO over CFL would outweigh this loss to a certain point though.

This can be overcome if you have a dedicated fish room, or enough space to make a vertical T5HO scrubber, like this:

And to my knowledge, those endcaps are no longer available, or else I would totally be using them.


LEDs are a completely different source of light. Fluorescent, metal halide, HPS, and other HID lighting are all mercury based, and the light is shifted from the ultraviolet range into the visible range with phosphors. LEDs emit certain colors of light depending on the compounds used in the diode itself, so it is initially visible light; phosphors are then sometimes used to shift wavelength to achieve various colors.

Generally speaking, LED lighting has advantages over other type of lighting. The most obvious one is lamp life – they never actually burn out (unless you drive them too hard). LEDs have what is called an L70 (or L80) rating, which is the number of hours, running at rated junction temperature, at which the lumen output will have dropped to 70% of its original output. At this point in time, that is usually about 50,000 hours. If they are on 18 hours/day, that’s about 7.6 years to L70. Some negative factors for LED are the long-term phase shift and the effect of steadily decreasing output. Phase shift is the reason that most small municipal airports are avoiding LED lighting: white LEDs are actually blue with phosphors added, and they ‘fade’ over time, and shift to blue. Runway lights are white, taxiway lights are blue, and getting them confused is bad. The LED industry is rapidly evolving, so the L70 numbers will continue to increase, cost will decrease, and issues like phase shifting will likely be improved upon.

But at the current state, there is a decent mathematical reasoning for going LED. Just using T5HO lamps as a baseline, let’s say you need 4 24W lamps ever 3 months for a 100 gallon scrubber, each costing $4 each. That’s $64 per year, and over 7 years, that’s $448. If you use 23W CFLs and you can find a stellar deal on them, you might be able to get them for $1 each, or about $112 over 7 years. So the cost of designing and building and LED fixture falls somewhere in between the two, IMO. If you DIY it, the material will cost you a couple hundred bucks, and the design time you’re going to spend either way, so most of that is offset.

The desired spectrum can theoretically be tuned to exactly what you need. This means that you can potentially overpower a scrubber if you use the same wattage as you would use for a CFL or T5HO scrubber, and just like you can bleach your corals with too much light, you can bleach algae with too much light. Also, it is important to note that there has been no study that I could find that indicates what exact LED spectrum is ‘perfect’ for algae growth for this specific purpose. At this point, you probably should not rely on an LED scrubber for total filtration, only for supplemental filtration. There are many unknowns, but it has great potential.

There’s not a lot of information regarding how these factors will impact algae growth. The phase shift is probably the biggest factor that is not known. Although, anyone who builds their own LED fixture will likely want to build another, better one in 2 years when more efficient and cheaper LEDs come out. So if you feel up to building your own LED scrubber, at this point, I say knock yourself out. Just make sure you do your homework before putting pen to paper; study other designs and learn from the mistakes and successes of others.

Just make sure you realize that 1) LED scrubbers do not have a long track record to speak of, 2) only recently have there been builds with any sort of success, 3) they are still not tested for long-term stability and reliability.

The general consensus among those that have built multiple LED scrubbers (believe me, there are not many that have built more than one) are that at a minimum, you should use Warm Whites, and ideally you want to use 630nm Reds, or a combination of the two. The jury is out on the need for any blue at all, and the effectiveness of 660nm Deep Red might be offset by the fact that the 630nm Red is more intense and therefore more efficient. Remember, flow and light intensity trumps spectrum.

LED builds to date vary in size, shape, number and arrangement of LEDs, use of lenses and/or diffusers, and on and on. This one uses 630nm Reds, warm whites, and in the middle are a couple of 660nm 5W Deep Reds, and a 5W Blue. This one uses bare LEDs and a diamond diffuser plate to spread the light.

An off-the-shelf LED fixture is generally more expensive than a DIY job. For scrubbers, there are very few choices in LED off-the-shelf, it’s pretty much limited to plant growth lamps. There’s plenty of them out there, but they’re rather expensive and lots of them are made overseas, where they use cheap LEDs, under-drive them so they don’t blow, and put them in cheap housings that aren’t made for use anywhere near water. The American made fixture are much more reliably built, but the prices are coming down. It’s only a matter of time before LEDs are tried and tested.

Electrical Protection

This should really go without saying, but you should always plug your lights into Ground-Fault protected receptacles (GFCI). You should actually have all your equipment plugged into GFCI receptacles, and on as many separate circuits as feasible – but that’s another discussion.

Always use waterproof sockets for your CFLs and end caps for your T5HO lamps. This is a little more expensive, but is necessary to avoid corrosion and electrocution. Generally, waterproof CFL sockets do a pretty good job of sealing the base and socket from moisture, but they still should be silicone sealed for an extra layer of protection. T5HO waterproof end caps do an excellent job of sealing the end of the lamp, but the wires that feed into the bottom of the sockets are not sealed, so after all wiring is complete, you need to fill in the bottom with silicone caulk.

You can’t see it, but there will be tiny amounts of salt spray that will build up where you screw a CFL bulb in, and also where you make electrical connections. When the buildup gets thick enough, it can short out and trip a breaker or GFCI receptacle, or shock you. So each time you replace a CFL screw-in lamp, re-seal it. You should be able to pour water over it without it causing a problem (but don’t try it). Use GE Silicone I Door & Window caulk, which is generally accepted as aquarium safe, especially since you don’t intend for it to be in direct contact with water anyways.

Spray Protection

As far as spray and salt creep is concerned, you want to avoid buildup on the lamp itself. No matter what you do, there will still likely be some buildup due to evaporation, so you will want to wipe off the lamp periodically (as needed). Make sure the lamp is completely cooled down before wiping the lamp off, remove the lamp if possible, and wipe it down with a soft cloth and warm to hot water. This is rather easy to do in place with T5HO lamps, and more difficult for spiral and multi-tube CFLs; just be gentle so you don’t crack the tube.

The water will cascade down the screen smoothly, and then drop off the bottom edge. If you don’t let the bottom of the screen sit in the water, it’s going to pour off and crash down, and splash everywhere. That’s not the problem I’m discussing here, I’m talking about spray from the slot pipe or screen.

The ideal solution is to block the source of salt creep or spray – the slot pipe itself. While 99.99% of the water that cascades down the screen will stay on the screen, occasionally there will be droplets of water that pop and fly around, and over time these can cause salt creep. If you have a lot of spray on a consistent basis, then you have a different problem – this generally should not happen, and will be covered under the troubleshooting section in Part 2.

The best spray blocker is a box that totally encloses the screen on all 4 sides and bottom, and has a removable lid. Such a box would have a drain hole in the bottom, and would typically be made out of acrylic, but could be made from glass also. This is beneficial for other reasons too, but we’re just talking spray blocking right now. If you go this route, you want to read the section regarding enclosed boxes in Part 2 for more details – which is coming, I promise!!

Closing the top with a lid, or at least extending the blocker up to the top of the slot pipe, will minimize the random drops that occasionally fly upward, as well as evaporation. A lid should not lip over the outside of the box, rather the inside so that any condensation will tend to stay inside the box.

The next best would be an enclosure with an open bottom. The advantage to an open-bottom enclosure is that it’s easy to build. If you extend the screen to the water level inside the sump, you virtually eliminate noise and microbubbles. Pictures illustrate this best:

I don’t recommend enclosing CFLs in glass jars. IMO, it is difficult to allow for adequate air convection with such an arrangement. I don’t recommend using plastic bottles either. CFLs get hot; you can’t touch them when they’re on. If the lamp gets in contact with the plastic, it could melt.

End of Summary #1

As mentioned at the start of this summary, I will write up “Part 2” which will cover various troubleshooting pointers, enclosed boxes, growth types, customizing to your specific system, overflow protection, increasing flow, operation, maintenance, cleaning, etc

If you have any suggestions or corrections, please post them or shoot me a PM and I will note them for future summary posts.

New sizing guidelines

New Scrubber Sizing Guideline (Sept 2011)

Scrubbers will now be sized according to feeding. Nutrients “in” (feeding) must equal nutrients “out” (scrubber growth), no matter how many gallons you have. So…

An example VERTICAL waterfall screen size is 3 X 4 inches = 12 square inches of screen (7.5 X 10 cm = 75 sq cm) with a total of 12 real watts (not equivalent) of fluorescent light for 18 hours a day. If all 12 watts are on one side, it is a 1-sided screen. If 6 watts are on each side, it is a 2-sided screen, but the total is still 12 watts for 18 hours a day. This screen size and wattage should be able to handle the following amounts of daily feeding:

1 frozen cube per day (2-sided screen)
1/2 frozen cube per day (1-sided screen)
10 pinches of flake food per day (2-sided screen)
5 pinches of flake food per day (1-sided screen)
10 square inches (50 sq cm) of nori per day (2-sided screen)
5 square inches (50 sq cm) of nori per day (1-sided screen)
0.1 dry ounce (2.8 grams) of pellet food per day (2-sided screen)
0.05 dry ounce (1.4 grams) of pellet food per day (1-sided screen)

High-wattage technique: Double the wattage, and cut the hours in half (to 9 per day). This will get brown screens to grow green much faster. Thus the example above would be 12 watts on each side, for a total of 24 watts, but for only 9 hours per day. If growth starts to turn YELLOW, then increase the flow, or add iron, or reduce the number of hours. And since the bulbs are operating for 9 hours instead of 18, they will last 6 months instead of 3 months.

HORIZONTAL screens: Multiply the screen size by 4, and the wattage by 1.5

Flow is 24 hours, and is at least 35 gph per inch of width of screen [60 lph per cm], EVEN IF one sided or horizontal.

Very rough screen made of roughed-up-like-a-cactus plastic canvas.

Clean algae off of screen every 7 to 14 days, so that you can see the white screen material.




Scrubber Quick Guideline
Scrubber Basics
Scrubber Configurations
Scrubber Lighting
Scrubber Flow
Scrubber Materials
Scrubber Results
Scrubber Comparisons
Scrubber Applications
Scrubber Advanced Topics
Scrubber Miscellaneous

Scrubber Quick Guideline:

0.5 actual (not equivalent) fluorescent watts per gallon MINIMUM [0.13 watts per liter].
1.0 actual (not equivalent) fluorescent watts per gallon for HIGH filtering [0.26 watts per liter].
1.0 square inches of screen per gallon, with bulbs on BOTH sides (10 x 10 = 100 square inches = 100 gal)
[1.64 square cm per liter]
2.0 square inches of screen per gallon, if vertical but lit on just ONE side. [3.28 square cm per liter]
4.0 square inches of screen per gallon, if HORIZONTAL [6.56 square cm per liter].
1.5 actual (not equivalent) fluorescent watts per gallon if HORIZONTAL [0.4 watts per liter].
18 hours of lights ON, and 6 hours of lights OFF, each day.
Flow is 24 hours, and is at least 35 gph per inch of width of screen, EVEN IF one sided [60 lph per cm].
Very rough screen made of roughed-up-like-a-cactus plastic canvas.
Clean algae off of screen every SEVEN (7) days NO MATTER WHAT YOU THINK.

Scrubber Basics:

Q: Who owns AlgaeScrubber.Net?
A: His name is Tom Worley. He is in the U.K.

Q: Who is SantaMonica?
A: He is a reef tank owner in Santa Monica, California, USA. He is an electrical engineer by schooling, but currently works in promotion and marketing. A fish tank was originally suggested to him by one of his interns in his office, as something that would fill some space in a hallway. He hired a maintenance guy to do everything, and this guy killed everything. A second guy was hired, who killed everything again. So finally SantaMonica started reading the many forums, and decided that an algae scrubber would work great to help solve these problems. He posted his plans and info for how to build them, and thousands of people did. This FAQ is a results of what these people found.

Q: What are algae scrubbers?
A: Algae scrubbers are not brushes! Scrubbers are devices which use light and flowing water to remove the “bad” things (nutrients) from aquarium water, while leaving the “good” things (food, nutrition) in. Unlike the scrapers/scrubbers that you use to clean your glass, an algae scrubber does not physically clean anything. Instead, the “scrubbing” is when the “dirty” water passes through an algae scrubber, and then the “clean” water comes out. The water is thus “scrubbed” clean of nutrients (nutrients are “bad”, but nutrition is good).

Q: What are these scrubbers called?
A: They are called Scrubbers, Algae Turf Scrubbers (ATS), Algae Scrubbers, Algae Filters, Turf Scrubbers, Turf Filters, and Turf Algae Filters. They are all the same thing.

Q: Do I need one?
A: If you have nuisance algae growing in your tank, then an algae scrubber will remove it.

Q: Will a scrubber cause more algae to start growing in my display?
A: No. A scrubber will only remove algae from your display.

Q: How long does it take to get results?
A: Typically, your nitrate, phosphate and nuisance algae will start reducing after you have cleaned off a full screen of algae three times. However, even if you clean the screen properly (weekly), it may take a few weeks for the screen to become completely full for the first time. On average, most people solve their nitrate, phosphate and nuisance algae problems within eight weeks, and some people who have very strong lights (within 4″ (10cm) of the screen) do so within four weeks. Strong lights, good flow, a VERY rough screen, and weekly cleanings are the keys.

Q: How big of a scrubber do I need?
A: Start with one square inch (6.25 square cm) of screen, with a light on both sides, for every U.S. gallon (3.8 liters) of water in your display tank. Thus, a 100 gallon display tank would need a screen 10 inches by 10 inches (100 square inches), with a light on both sides. If you can only put a light on one side, then you need to double the screen area, and also double the lighting on the one side. You don’t need to include the volume of the sump, unless it also has livestock in it that you feed.

Q: Can I build a small scrubber just to see if it works, before I spend the time to make a properly-sized one?
A: The only thing a “too small” scrubber will show you is that it will grow algae. It will not show you that it can filter, because it will probably only grow dark algae, due to the scrubber not big enough to get the nutrients down so that it can grow green algae. In other words, filtering is not linear: A scrubber half the size does not do half the filtering; it does much much less filtering. That’s the reason for the recommended sizes: They are the sizes where the filtering really starts to happen. So no, you should not start with a too-small one.

Q: Will a scrubber harm my corals?
A: No. Matter of fact, corals grow best with lots of food particles (nutrition) in the water, and corals also like low levels of nitrate and phosphate (nutrients). That’s exactly what scrubbers provide. This applies especially to SPS corals.

Q: Will a scrubber work in freshwater?
A: Absolutely. Same benefits, similar to plants, but in a more compact space. Scrubbers are not for “planted-only” tanks, however, because the scrubber would compete with the plants for CO2.

Q: Are the scrubber requirements any different for a fresh water tank?
A: Since you don’t have to worry about coral growth, and also since you don’t need to grow coralline like somebody with a salt water fish-only/live-rock tank might want to do, you do not need to be concerned about phosphate. Your only concern is ammonia, nitrite and nitrate. Therefore you can have, or add, extra phosphate in order to keep the ammonia, nitrite and nitrate low. Algae needs both phosphorus and nitrogen to grow, but if there is “zero” phosphate in your tank, then the algae in the scrubber won’t grow enough to remove the nitrogen (which is found in the ammonia, nitrite and nitrate). 1.0ppm of phosphate should make sure that there is more than enough, so that the scrubber has all the phosphate it needs, and can therefore work on removing the ammonia, nitrite and nitrate. An easy way to add phosphate is to get some Mono Potassium Phosphate (one source is and dissolve a spoonful of it into a cup of FW. Add a little of the water to your tank, and test for phosphate again. Repeat until the level is 1.0ppm phosphate.

Q: I’ve heard that scrubbers will cause your water to turn yellow.
A: Not if cleaned in your sink. Yellowing is caused by cleaning the screen while it’s still in your system (the broken algae drains into your water). Cleaning weekly, in your sink with tap water, solves the yellowing that occurred for 20 years in previous scrubbers.

Q: Are scrubbers noisy?
A: Not when built properly. The screen should go into the sump water slightly, and the water should flow smoothly down the screen, with no spraying, splashing or noise. Your pumps should be the only thing you hear.

Q: Do they smell?
A: When running, they do not smell at all. This is because they always have water flowing over them. When cleaning them in your sink, there is an “ocean” smell. Nothing as bad as cleaning a skimmer though.

Q: I’m currently building my tank. Should I wait to install my scrubber?
A: No. The screen won’t grow a lot, however, until you actually start feeding.

Q: I’m still designing my system. What other filtering devices besides a scrubber should I get?
A: Since you don’t have filters set up yet, why not start with just a scrubber, and then monitor your nitrates and phosphates weekly as you add livestock. If you reach a point where your scrubber can no longer keep nitrate and phosphate at undetectable levels, you can then decide to either build a larger scrubber (or improve your current one), or buy other filtering devices. A powerful enough scrubber, however, can handle any size tank/fish/coral load. Algae is 90 percent of the real ocean, and does all the filtering and feeding for it.

Q: Are water changes still needed if I use a scrubber?
A: If the purpose of the water change is to reduce nitrate or phosphate, or to help reduce nuisance algae in the display, then no. If the purpose of the water change is for anything else, like removing medications, then yes.

Q: Where can I buy a scrubber?
A: A 100 square inch model is now available on the AlgaeScrubber.Net site.

Q: Can someone build one for me?
A: Any acrylic shop should be able to. There is also a list of willing builders here:

Q: What’s the most important thing that I need to pay attention to when building my scrubber?
A: The screen. It needs to be ROUGH.

Q: Do I need to “seed” my screen with algae to get it to grow?
A: No. All screens will grow by themselves. Seeding (rubbing algae into the screen to get it started faster) is no longer recommended because is just does not speed things up enough, and it just puts extra waste into the water. If you want your screen to grow faster, then make it rougher by scraping a hole-saw (not in a drill) across the plastic canvas. The screen should feel like a cactus, and be too rough to rub on your face. The rougher it is, the faster algae will grow on it, and the longer the algae will stick to it.

Q: How do you clean a scrubber screen?
A: You clean it every 7 days, by removing the screen from the scrubber, taking it to your sink, and running tap water over it while removing the algae. Don’t remove all the algae, however, because you want it to grow back quickly, and also because you need some algae to continue to do the filtering. So leave a small layer of algae on the screen. The rougher your screen is, the more algae will remain, and thus the faster the filtering will start again. If you have two separate screens, then you can clean one completely down to the plastic, since the other one continues the filtering. Also, if your screen is two layers (like a sandwich), you can also clean down to the plastic, since algae will remain between the two layers.

Q: How often do you clean it?
A: Once a week (7 days), NO MATTER WHAT. This is probably the biggest hassle with scrubbers, and when it is not followed, it’s THE biggest reason why a scrubber is not working as good as it should. When the algae gets too thick on the screen, it blocks the light from getting to the bottom layers. Thus the bottom layers die, and they put nitrate and phosphate and cloudiness into the water. Weekly cleaning eliminates this. If your screen is smaller than it should be, or if your nutrients are very high in your tank, your screen might fill up and need cleaning in just a few days. This is ESPECIALLY true if the screen is growing dark, oil-like algae. This type of algae will never get thick because it blocks out all the light, so it must be cleaned as soon as it grows. After the nutrients in your water come down, the dark algae will grow less, and the green algae will grow more (dark algae is caused by very high nutrients.)

Q: I have a fish-only tank with large fish, and I don’t care about small food particles floating around in the water. Do I need a scrubber?
A: Maybe not. If you don’t mind cleaning the nuisance algae off the glass (which is caused by Inorganic Nitrate and Inorganic Phosphate in the water), then a skimmer may be fine. But if you are trying to reduce nuisance algae (and glass cleaning) then you’ll need a scrubber in addition to a skimmer, because a scrubber removes the Inorganic Nitrate and Inorganic Phosphate (which is what algae feeds on).

Q: I’ve heard that going “skimmerless” is only for experienced aquarists.
A: That was correct before August 2008. But it is now known how to easily build and use a scrubber to do all your filtering for you (just like algae does ALL the filtering and feeding in the ocean). It is cheap, easy, and best of all there is NO possible way for something to “go wrong” with a scrubber which would cause it to kill your whole tank (skimmers, however, can overflow the cup and kill everything because of the ammonia build up). So scrubbers actually are now the entry level (beginner friendly, and cheap) way to start out.

Q: Are scrubbers dangerous, since they have electricity and water so close together?
A: They are as safe as you build them to be. Think about aquarium pumps, which have the power cord actually going in the water; since they are built for it, they are safe. Some recommended safety tips for building and using scrubbers are: Use GFCI power outlets; Use aquarium-safe silicon on all electrical connections; seal the bulbs into the sockets, and cut them out with a razor blade when you need to replace them; turn off the scrubber lights when cleaning the screen (if you must reach into a scrubber while the lights are on, use only one hand, and keep the other hand in your pocket); ventilate sump areas that are enclosed; identify what will happen if water sprays from the pipe (and use a cover if needed).

Q: Why have scrubbers caused so much anger by so many people?
A: These people are angry because:

1. They are employed by, or they are a relative/friend/spouse of someone who is employed by, a manufacturer/distributor/retailer/installer of skimmer/filtration/waterchange/additive products. There are over 3,000 stores in the U.S. alone that sell these products, with several people working at each one. That’s a lot of people to post anti-scrubber comments online. And they are paid to do it.

2. They have a lot of money invested in their skimmer and other filtration equipment. So they feel ripped off to find that a cheaper piece of equipment can do a better job of removing nutrients. It makes them look unprepared.

3. They had aquariums in the 1980’s, 1990’s, or early 2000’s, when scrubbers were built and operated incorrectly. Scrubbers back then were noisy and caused yellowing and clouding. Scrubbers today don’t. But these people have not used a modern (after August 2008) scrubber, so they think all scrubbers still operate the same.

4. They don’t understand how scrubbers work, and they are not going to learn. They think that skimmers remove Ammonia, Nitrite, Inorganic Nitrate, Inorganic Phosphate (i.e., all the bad stuff). But skimmers don’t do this. Not even a little. Scrubbers do.

5. Since they already have a setup that works properly, they have no reason to expend the time and energy to change. This is understandable.

Scrubber Configurations:

Q: What is the best type of scrubber to build?
A: For most new aquarists, simple and cheap scrubbers are best. Simple configurations are just a screen hanging in a sump. For intermediate aquarists, compact size and better performance might be wanted. These configurations might be custom built acrylic units, with very bright lighting. For advanced aquarists, compactness is usually not a concern, but strong performance, and redundancy of lighting and flow, is. So a dual or triple screen, dual-pump, multiple-light configuration would be best.

Q: Where should I place the scrubber in my system?
A: Theoretically, the “best” for a reef tank is to have the scrubber above the display so that all the pods can drain into the display unharmed. But if the goal is just to remove nitrate, phosphate and nuisance algae, then it doesn’t matter where you put it.

Q: Besides the designs like the screen-in-the-sump, the acrylic box, and the top-of-the-nano-tank, are there any other options for special situations?
A: Certainly: Circular, horizontal, trough, dual-screens, hang-on-wall, recirculating, display-light powered, and overflow feed, not to mention solar powered.

Q: Is a vertical or horizontal screen better?
A: Vertical is better. It is proven, and it is the smallest and most powerful for a given amount of space, flow, and lighting. Horizontal is OK if you want to experiment, but if you absolutely must have results, go vertical. The biggest operational problem with horizontal is that as algae builds up on the screen, it blocks flow to areas downstream from it. This is because the water is not flowing very fast, and it cannot “jump” up and over the new growth. So the more algae, the more blockage, and thus it is self-limiting unless you have a LOT of flow. With a vertical, however, the flow is rapid and goes right over new growth. This is the reason that a horizontal needs 4X the screen area, so it can make up for less performance.

Q: What advantages are there to wide screens? If a screen is narrow, but taller, and has the same area, isn’t it the same?
A: No. The big difference is in the amount of water processed; A screen twice as wide will flow twice as much water, and this makes a big difference in how fast it can eat the nutrients out of the water. Also, if part of the slot gets blocked by something, a wider screen will not be affected as much as a narrow screen.

Q: What are the recommendations for a screen that is horizontal?
A: People who have had success with horizontal designs have done so by having four times (4X) the screen size, and 1.5 fluorescent watts (not equivalent watts) per gallon. For example, a 100 gallon tank (380 liters) would need 400 square inches (2500 square cm) of screen, and 150 real watts of light, to be really effective.

Scrubber Lighting:

Q: What kind of light do I need?
A: Experience has shown that at least a 23 Watt Compact Fluorescent (CFL) bulb, of the 2700K or 3000K (“warm” or “soft”) color, works best. One on each side of the screen, about 4″ from the screen, and pointed to the middle of the screen. And note that 23W is “at least”, unless it’s for a nano. These CFL lights have also shown to only last about three months before their power drops off, even though they “look” fine. T5HO bulbs have also shown tremendous scrubber growth, although they are more difficult to design and build; their spread of light from side to side is superior to CFL bulbs. There is an upper limit to CFL bulb size; CFL bulbs in the 45 watt range are at the top, whereas anything higher than that will tend to “cook” the screen in one spot. If you must have more than 45 watts per side, use two smaller bulbs instead. The lighting just needs to be spread out more evenly, and not so concentrated in one spot. If you use CFL bulbs and they are not floodlights (which have built-in reflectors), be sure to get “CFL reflectors” so you can reflect the light to the screen.

Q: What if I can’t fit a light on both sides of the screen?
A: Then double the screen size, and double the lights on the one side. Doubling the screen size without doubling the lighting, however, does no good.

Q: I can’t find the “K” numbers on the bulbs I want to buy; Can I use “soft” or “warm” bulbs?
A: Yes, the “soft or “warm” bulbs, which are the most popular types for the typical home, are about 2700 or 3000K and they work the best. Even “full spectrum” or “daylight” bulbs are OK. The ones which don’t work the best are “cool” bulbs. But they still work.

Q: Can I use LEDs for lighting the screen?
A: LEDs are still being experimented with for use on algae (which is different from using LEDs for a display.) Thus they are not recommended if you absolutely want results. If, however, results are not as important as “experimenting”, then by all means try LEDs, but make sure they are as powerful as possible. A few watts here and there will not be enough. You want “reds” (670nm) and “blues” (420nm), in the high-power variety. Several horticulture and hydroponics sites sell ready-to-use LED panels and strips, which may work. You’ll want as much power for the LEDs as you would for the CFL bulbs, i.e., 20 to 50 watts per side.

Q: Can I use solar power on the screen?
A: Yes, if you have many days of sun throughout the year. The screen will, in effect, be one-sided, so you’ll need 2X the size (and if it’s horizontal, you’ll need 4X). It might be a good idea to still have a regular secondary or portable scrubber inside your house, in case of long lasting storms or winter days. You may also consider using a reflector (like aluminum or mylar) on the backside of the solar scrubber, and using lights on it for nights and/or backup.

Q: Are halides too strong for a scrubber screen?
A: They are not too strong, but they are very hot. So it’s currently advisable to not use halides. Scrubbers do not need the deep penetration of light into water that displays need; scrubbers instead need light that is spread out evenly across the screen.

Q: How long do I wait before replacing the bulbs?
A: CFL bulbs should be replaced every 3 months. T5HO/PC bulbs every 3 to 6 months. Do NOT wait longer just because “they still look fine”. You’ll see, after you replace them, how dim they really were compared to the new ones. Leaving old bulbs in a scrubber can completely stop it from working.

Q: How near do the lights need to be to the screen?
A: CFL bulbs should be within 4 inches (10cm) from the middle of the screen. If you cannot get the light nearer than 6 inches (15cm), then do some reconfiguration. Don’t build a scrubber at all if you can’t get the light to within 6 inches (15cm). T5HO bulbs can be within 1 inch (2.5 cm) of the screen, but 2 inches is OK. Algae needs LIGHT POWER to grow.

Q: What’s the best wattage/power bulb to use?
A: Generally, up to 45 watt CFL bulbs. The more powerful the light, the faster your nitrate, phosphate, and nuisance algae will be reduced, and the lower they will stay. The bare minimum for any setup is a 23W CFL Floodlight, 2700K or 3000K. A maximum might be a 45 watt bulb, but it’s better to have multiple smaller bulbs in order to reach your recommended total wattage. The ultimate are T5HO bulbs, which spread the light out so that the most light-power can be placed near the algae, without “burning” it in one spot like a CFL.

Q: I have some extra lights that I was using for my display; can I use those?
A: Only if they are 6500K or less. 10K is problematic. 14K and 20K will not work at all. And the power on each bulb still needs to be at least 23W, on each side of the screen.

Q: What’s the best bulb color/spectrum?
A: The best would seem to be the “plant grow” spectrum. These bulbs looks “pink”, and don’t seem bright at all. But 2700K and 3000K seem to grow even better. No special testing has been done for this, however.

Q: How long should I leave the lights on?
A: 18 hours. Never run the lights 24/7, because the algae will “burn” and stop growing near the light. Algae needs rest. Amazingly, algae does most of it’s filtering in the dark; it just grows bigger in the light.

Q: I see many times that people try a certain bulb, and then they are told it’s not the right one. What bulbs should I not use?
A: Don’t use incandescent, blue or green “plant lights”, desk lamps, reading lights, heat lamps, halogens, black lights, colored lights, actinics, bug lights, or fog lights. Do use CFL floodlights or T5HO bulbs, in 2700K, 3000K, or “grow” (pink) spectrums.

Q: If my tank and scrubber are large, then how do I know how much wattage to have on each side of the screen?
A: The basic goal is to have 1.0 watt of light for every gallon (3.8 liters) in your system for high filtering. And the basic minimum is to have 0.5 watts per gallon. So if your tank is 500 gallons, your goal would be 500 watts (total of all bulbs) of CFL or T5HO on your scrubber, and the minimum would be 250 watts.

Scrubber Flow:

Q: How much flow do I need on the screen?
A: At least 35 U.S. gallons per hour (gph) (133 lph) for every inch (2.5cm) of width of the screen. Thus a screen one inch wide would need at least 35 gph, and a screen two inches wide would need at least 70 gph, etc. More is even better. Less flow means less performance, and parts of the screen may go dry. And if you are making a horizontal screen, you then want ALL the flow on the one (top) side. This is because fast flow is critical, and horizontal screens do not have fast flow. So you make up for this by putting all the flow from a two-sided screen onto the one top side of a one-sided screen. And in all screens, flow will be limited by the roughness of the screen, because a smooth screen will let go of algae sooner than a rough screen will.

Scrubber Materials:

Q: What’s the best material to make the screen out of?
A: The overall best material is “plastic canvas”, which can be found at any craft/sewing store, and online at hundreds of places. It’s cheap, strong, and does not wear out. However it’s smooth and it’s made out of non-stick plastic, so to make it work the best, you need to rough it up using a hole-saw in your hand (not in a drill) so that it feels like a cactus. The rougher it is, the quicker the algae will grow, and the thicker it will grow without falling off, and thus the less nitrate, phosphate, and nuisance algae you will have in your display. Just remember that the more algae that can grow/stick on the screen, the less algae you will have in your tank.

Q: Can I use window screen?
A: No. That type of screen sometimes has chemicals to reduce mildew. Plus, it’s too flimsy, and it cuts/breaks too easily. And sometimes it’s metal.

Q: Can’t I just rough up a sheet of acrylic?
A: No. It’s not nearly rough enough.

Q: I saw some people using clear tubing for the pipe; won’t this grow algae in the tube?
A: Yes, and the algae will block the slot. Don’t use clear.

Scrubber Results:

Q: What can I do to get the best results from my scrubber?
A: When building, use the most wattage that you can, and put the bulbs within 4 inches (10 cm) of the of the screen. Preferably, use T5HO bulbs within 2 inches of the screen. When operating, clean the screen weekly, no matter what, using tap water in your sink. Clean sooner if the algae is dark brown or black. Replace the bulbs every 3 months, and watch the pump to see if it starts reducing flow. Make your screen VERY rough. And make the flow rapid across all parts of the screen.

Q: I heard that you have to watch out for “oil slicks” on your screen.
A: An “oil slick”, or very dark or black algae, usually happens when a scrubber is first set up on a tank with very high nutrients. This type of algae does not get thick, and it doesn’t even look like algae. The problem is when the person thinks that his screen is “just not growing yet”, and he leaves the screen alone (not cleaning it) in order to “give it more time to grow”. BIG MISTAKE. What actually is happening is that this particular type of algae is already fully-grown on the screen. And since it’s very dark, the outer layers block ALL the light from the inner layers, even though the algae is only 1/4 inch (6mm) thick. So the inner layers die and go back into the water, adding nutrients back. So the person leaves the screen alone even longer “to give it even more time to grow”, but the new outer layers once again kill the inner layers. The screen never gets “thick” like the person wants, and so the person never cleans it. Nutrient levels stay the same in the tank (and the water gets cloudy because of the dying inner layers), and the person feels that the scrubber is not working at all. The solution is to clean any and all dark/oily algae off as soon as it grows, EVEN IF it’s just two days old. This will bring nutrients down, and after a few weeks of doing this, green hair algae will start to grow. At this point you can switch to normal weekly cleaning.

Q: All I seem to get on my screen is brown slime. Must I have green hair algae?
A: No. All algae takes nutrients out of the water. They are just different types of algae depending on how high your nutrients are in your water, and how strong your lights are. Continue the weekly cleanings (twice a week if the algae is dark brown or black), and eventually you will get green. If not, try a stronger light, and possibly, stronger flow. If you never get green growth, your scrubber is just not strong enough for the amount you are feeding your tank. But you may still be happy with the results. Or, your scrubber may need “kick starting”, which is just helping it out by using extra lights until the scrubber starts growing green.

Q: I’m not getting good flow out of the slot in the pipe, especially when the screen fills up with algae. What can I do?
A: Add a light-shield on the pipe which keeps light from reaching the slot. Plastic opaque tape, or a piece of long plastic, works. Ideally though, you should clean the screen when the algae gets that thick.

Q: My scrubber smells. Is this normal?
A: No. It means your water flow is too low, which lets some of the algae touch the air. Increase your flow, or widen the slot. If you still can’t get enough flow, make the screen shorter (with a new shorter pipe), so that the flow that you do have will really cover the whole screen.

Q: I’m getting cyano on my screen. Is this good?
A: No. It means your light is too weak or too far away. Regular algae (green, slime, brown) should be the only thing that is growing, but it can’t grow if the light is too weak.

Scrubber Comparisons:

Q: How is a scrubber different from a skimmer?
A: Scrubbers remove Inorganic Nitrate, Inorganic Phosphate, ammonia/ammonium, metals and CO2 from the water. (Inorganic Nitrate and Inorganic Phosphate are what cause nuisance algae to grow on your rocks and glass, and are what you measure with your test kits.) Skimmers remove organics (protein/food) from the water. Both scrubbers and skimmers, however, add oxygen to the water. Scrubbers add more though, and can supersaturate the water with oxygen, due to photosynthesis.

Q: How does a scrubber compare to a refugium with macro algae?
A: This is a long one, and is detailed here:

Q: How does a scrubber compare to a coiled denitrator?
A: A denitrator removes nitrate, and may reduce the pH. A scrubber removes nitrate, nitrite, ammonia/ammonium, phosphate, CO2 and metals, and does so while increasing the pH. Also, a scrubber cannot harm a tank, whereas some denitrators, if adjusted improperly or if they malfunction, can put harmful chemicals into the water.

Q: How does a scrubber compare to GFO (granular ferric oxide) phosphate removers like RowaPhos and PhosBan?
A: GFO’s remove phosphate and silicates, and may lower the pH while doing it. And they are expensive to refill. Scrubbers remove phosphate, as well as nitrate, nitrite, ammonia/ammonium, CO2 and metals, and do so while increasing the pH. Scrubbers do not remove silicates. And once built and installed, scrubbers do not need to be “refilled”. Also, if a GFO bag or canister spills, or if you accidentally drop GFO into the water, it will go everywhere throughout your sump/pumps/tank. If you drop algae in the tank, it’s no different from algae that’s already floating in the tank, or from feeding nori.

Q: How does a scrubber compare to a Remote DSB (RDSB)?
A: RDSB’s removes Ammonia/Ammonium, Nitrite and Nitrate. Scrubbers remove the same, in addition to phosphate, metals and CO2. RDSB’s, however, just like regular DBS’s, tend to store phosphate in the sand during high-nutrient times. It then releases the phosphate back into the water during low-nutrient times (and this is when algae grows on the sand). Scrubbers don’t “store” phosphate; the phosphate is “in” the algae that grows, and it is then removed during the weekly cleanings.

Q: How does a scrubber compare to vodka (carbon) dosing?
A: Both remove nitrate and phosphate. Vodka, however, requires a skimmer to operate (to remove the bacteria that grows), and the skimmer thus also removes food (protein) from the water. Vodka also reduces the oxygen in the water (bacteria use oxygen), and if you add too much vodka you will see your fish breathing hard. Scrubbers don’t require (and work best without) a skimmer, and add oxygen to the water. Lastly is the safety issue of vodka: If you carelessly pour it from a bottle, “just a few ounces too much” can kill your entire tank in a few hours. With a scrubber, there is nothing that can happen which would cause such a situation. Scrubbers cannot kill your tank under any situation, even if you try. It’s just algae.

Q: How does a scrubber compare to bio balls (wet/drys)?
A: Bio balls (trickle, not submerged) aerate the water, convert ammonia to nitrite/nitrate, and trap pieces food (causing more nitrates). Scrubbers aerate the water, consume ammonia, nitrite, nitrate, phosphate, metals and CO2, add oxygen and millions of baby copepods, raise pH, cool the water if you put a fan on it, do not trap food, and weigh nothing (does not hold water), and thus can be outside the cabinet, or on top of the tank.

Q: How does a scrubber compare to an ultraviolet sterilizer?
A: A UV kills ick, and other parasites and live food that are in the water. A scrubber reduces nitrate, ammonia/ammonium, phosphate, grows pods, cools the water, increases pH, increases oxygen, allows live plankton to feed the corals, removes metals, stabilizes pH on a reverse photoperiod, and works without a skimmer. However a scrubber does not kill ick, and that might be reason enough to have a UV that you can turn of when you add new fish (and turn off after).

Scrubber Applications:

Q: Can I put a scrubber on my nano?
A: Yes, you can make/put a scrubber on any tank, or any body of water for that matter. There are three types of nano’s: Those with a hatch on the top that let you get to the filter area without opening the lid, those where there is no hatch (like Aquapods) where the whole lid opens up as one unit, and those with no hatch but where the “sump” area in the back is open on the top. The closed Aquapod types are the hardest to add your own scrubber to; whereas the hatch-on-top types are the easier. The open-sump ones are the easiest.

Q: Have scrubbers been used for breeder or retail tanks?
A: They are being tested now, and there have been several success reports using very heavy feeding.

Scrubber Advanced Topics:

Q: What exactly does a scrubber do to my water?
A: It takes ammonia/ammonium, nitrite, inorganic nitrate, inorganic phosphate, metals (like copper, aluminum and iron), and CO2 out of the water. It puts oxygen into the water. It also cools the water if you have an open-air design. And if you put a fan on it, it REALLY cools the water. Increased evaporation will also occur, unless you use an enclosed unit. Baby copepods (tiny white dust specs) are added to the water. Iron and Iodine are removed from the water. Alkalinity may in some cases be slightly decreased, because of algae’s slight use of bicarbonate to get CO2. Water clarity (meaning tinting, which is different from particles) is also sometimes improved, although it is not known why. Lastly, organic molecules are put into the water: Carbohydrates, vitamins, proteins, enzymes, lipids, and these amino acids: valine, leucine, tyrosine, phenylalanine, methionine, aspartate, glutamate, serine, alanine, and proline.

Q: I keep hearing “Yes, skimmers DO remove nitrate and phosphate! They just do it by removing organics BEFORE they break down into nitrates and phosphates”
A: That’s just great. Organics, before they “break down”, are called FOOD. Yes, FOOD. So yes, skimmers DO remove FOOD (i.e., “protein”). But saying that removing FOOD is the same thing as removing nitrates and phosphates is like saying that removing BEER before you drink it is the same as removing pee afterwards. Wouldn’t you rather have the beer, and remove the pee? Skimmers remove the food that you put in the tank, period. If removing food is what you need, then a skimmer is a must-have. Skimmers are recommended for fish-only tanks, especially with large predators.

Q: You say that algae removes CO2, and adds oxygen. But algae needs “respiration” time too, when it actually adds CO2 back to the water.
A: Yes algae adds CO2 back to the water when the lights are off. But it remove MORE CO2 when the lights are on, as long as the algae is growing. That is, after all, how the algae grows… it eats (accumulates) more nutrients than it releases. Otherwise the algae would shrink instead of grow. Algae takes carbon from the CO2, and uses it to build biomass. So it must take in more than it releases. The amount of CO2 it releases is actually very small.

Q: What if there is a power outage? Will my scrubber die?
A: In most cases you will loose your tank before you loose your scrubber. With no power (and thus no flow or light for the algae), the outer layer of algae hardens and keeps the inside layers wet. Six hours should not be a problem; just do a regular cleaning when the power comes back on. But twelve hours or longer, and you will probably loose your scrubber. But your tank will be gone too.

Q: I’ve heard that scrubbers “leach” or “leak” chemicals and cause a long term build-up of them, like toxins.
A: This is a three-part answer. First, the quick easy answer is no, what you heard is not correct. Second, algae uses light to create food: vitamins, amino acids, and sugars, which feed corals directly, and which feed bacteria that feed corals too. This is what is “leaching” or “leaking” out of the algae. But it’s really not leaching or leaking; it’s being manufactured by the algae, using light, and it’s needed to supply the food chain of the ocean. If you don’t skim out these vitamins, amino acids, and sugars, they will feed your corals. Third, they don’t “build up”. They are eaten quickly by corals, and by bacteria, which are then eaten by corals. If you have no corals, then they are just eaten by bacteria, and by the critters in your live rock.

Q: Is a skimmer or a scrubber better to cycle or cure live rock with?
A: First of all, many folks are not familiar with the differences between “cycling” and “curing”, so here is how you can know what to do, regardless:

If the rock was dry (meaning “dead”) when you got it, then there is nothing in the rock that you need to keep alive. So “dry” rock, no matter what it’s called, will not benefit from a scrubber (or a skimmer either). Preparing dry rock is easy because you WANT the ammonia to build up to high levels, so that the proper bacteria will build up in the rock. This bacterial will then remove ammonia when you put it in your tank.

“Wet” rock, meaning rock from the ocean or an established tank, is different. It DOES have live stuff in it, which is why it’s called “live rock”. You want this stuff to stay alive because it filters and feeds your tank. However, much of it died on the way from the ocean to you, and if you put a lot of this rock directly into your tank, you may get too much ammonia from it. So for larger amounts of rock, you want to “cure” it in a separate container. But here is where the super, gigantic difference between skimmers and scrubbers really shows: The living things in the rock are kept alive by food particles, but are killed by ammonia. So if you only have a skimmer on the container (which removes food, but not ammonia), you take away the food that the little animals need to live, and you let the ammonia stay, which further hurts the animals.

A scrubber, however, leaves all the food in the water, even if the “food” is dead and decaying stuff. This “stuff” is not harmful at all; it’s the ammonia that is harmful. The “stuff” is actually food for the critters that came with the rock. Scrubbers remove the ammonia (that’s what algae eats), so the critters in the rock will still have food to eat, without being killed by the ammonia. A skimmer, however, removes the food that the critters need to eat, but does not remove the ammonia. Thus the critters are starved, and killed, at the same time. So if the rock is “wet” and is supposed to be “live rock”, then using a scrubber instead of a skimmer will allow the rock to keep the most life possible, and in many cases will eliminate a “cycle” altogether.

Q: I’ve heard you have to “pulse” or “surge” the water to get best results.
A: This is not proven. Most scrubbers use a constant flow, and have great results. Thus it is not recommended to use a surge device. Plus, surges are noisy, and are just too difficult to build.

Q: What type of algae is best to grow?
A: You don’t have much choice; algae will grow based on lighting, flow and nutrients, and will even change as your nitrates and phosphates drop. All algae consume nitrate and phosphate, so it really doesn’t matter what type algae it is. What matters is how MUCH grows.

Q: Can a scrubber “crash”?
A: No. There is no situation in which a scrubber can “fall to pieces”, dissolve, disintegrate, or otherwise destroy itself and the tank that it’s connected to. The worse that can happen to your tank is that the scrubber light burns out and stays out for 2 or more days, in which case the algae will slowly start dying over the next week. You will just loose some filtering, and the water will get cloudy (just as if you were cleaning algae off of your rocks.)

Q: What kind of pods does a scrubber grow?
A: Supposedly copepods, amphipods, mini-stars, etc. However, because you clean the screen in tap water every week, all you really get are 7-day-old baby copepods that look like white dust. And you get millions of them, enough to feed several mandarins and scooters.

Q: How long does it take to get the real “red/brown” turf?
A: Several months. Maybe a year. All algae is good, however, no matter what color or texture it is. Real red/brown turf does not filter as much as a lot of green hair algae, however. Green hair algae lets the light and water flow through it, without blocking it. Thus, more algae touches the water, and provides more filtering.

Q: I’ve heard that scrubbers evaporate a lot of water.
A: The typical DIY scrubber in a sump will evaporate, and cool, the water. If you put a fan on it, it will REALLY evaporate and cool the water. Some people want this, others don’t. If you don’t, then enclose your scrubber in acrylic or plastic so that no air gets in. (And be sure to cover all electrical and bulb connections with aquarium safe silicone to protect them from salt buildup.)

Q: My scrubber has gotten rid of my green and brown nuisance algae in my display, but the dark purple cyano remains. Will it go away too?
A: Cyano is the last of the things to go away, because it can make its own nitrogen, and thus does not need ammonia/nitrate/nitrate to do it. So it may last a while, but if you keep nutrients low enough for long enough, it too will fade. However, it may be overpowered by coralline before this happens. Generally, it takes a very strong scrubber to get rid of every last bit of cyano.

Q: Since scrubbers don’t remove food from the water like skimmers do, won’t the DOC (dissolved organic carbon) build up and cause problems?
A: No. You need to realize that DOC is food also; it’s just microscopically small food, mostly eaten by bacteria, and by some corals. So the DOC gets to a certain level and stays there, since it’s being consumed by bacteria and corals. And the bacteria themselves are food for corals too. But also you need to know that recent research has shown that skimmers actually don’t remove (much) DOC as previously thought. Skimmers are mostly removing POC (particulate organic carbon), i.e. pieces of food. That’s why they are called “protein skimmers”, because food is protein.

Q: I’m getting micro-bubbles in my tank; how do I stop this?
A: Bubbles are usually caused by having the screen above the waterline, so that the water falls off the screen into the water. This is solved by making sure the screen goes into the water an inch or so. Another possible cause is that your slot in the pipe is too narrow, causing the water to be forced out. Try widening the slot (if your pump has enough flow.) If bubbles are still present, make an “under-over-under” pathway for water to go after the scrubber. Don’t use foam blocks, however, since they catch the pods and other food that you want floating around for the corals and small fish to eat.

Q: Sometimes my scrubber sprays sideways and gets things wet. How do I stop this?
A: If your screen normally flows properly, the sideways spraying is caused by not cleaning the part where the screen inserts into the pipe. Algae grows right up into the slot, causing the spraying. The solution is to clean up into the slot when cleaning, or (better) remove the screen from the slot entirely when cleaning it. To prevent it entirely, you can make a little “light shield” and attach it to the side of the pipe, in order to shade the top of the screen from light, and also to block any spraying that occurs. You can also just clean more off the top of the screen, so that there is a 1/2″ empty area with no algae at all just below the slot.

Q: Are two screens better than one?
A: Two separate screens allow you to clean one while leaving the other operating. This prevents nutrient “spikes” from occurring in your tank, because when you clean a screen you sometimes have very little algae left on it for filtering. Thus the other screen takes over. The trick with two screens is to make each one big enough (with enough light for each one) so that each one can do all the filtering by itself.

Q: Are multiple lights better than one?
A: Aside from just being brighter (which is always better), multiple bulbs give you a backup in case one burns out. It also give more even coverage of the screen from edge to edge. You almost can’t have too much light, as long as you have enough flow.

Q: I really want lots of pods; what can I do?
A: First make sure you have no (not one) mechanical filter in your system. This includes a skimmer, foam pads, floss, and filtersocks. All food and pods should be allowed to circulate forever. Next, before you take your screen out for cleaning, put it into your tank and swirl it around. This will release many pods into the tank (don’t shake hard enough to remove algae, though). After doing this, do your regular tap water cleaning in your sink. An advanced trick is to clean with SW, but this will not kill the pods, and thus you may need to clean more often. But you will have more pods.

Q: What is the single most important thing I need to know or remember about scrubbers?
A: That they must be cleaned every 7 days, no matter what the algae looks like.

Q: If I put a scrubber in my sump, will algae start growing all over the sump?
A: No. The lights of a scrubber are very near and pointed at the scrubber screen (4″ or less) for a reason: Light is only powerful when it is near. Thus the bulbs are too far from the other parts of the sump to cause algae growth. If you do get algae growing in your sump, then you need to get the bulbs closer to the screen, or, shade the sump from the bulbs.

Q: I’m getting a thin tar-looking growth on the screen, but it won’t grow anymore.
A: What you have is the type of algae that grows when nutrients are extremely high. After a few cleanings, the nutrients come down and the color will lighten up to some balance point where it will stay. The dark type of algae does not grow thick at all. It never gets more than 1/4″ (6mm) or so. And worse, since it’s so dark, it blocks all light from reaching the bottom layers, thus causing those layers to die and release nitrate and phosphate back into the water. The solution is to clean all dark brown/black algae within a few days, not even waiting until the end of the week. Basically, if you cannot see your screen because of the black algae, then light is not reaching the bottom layers, and it needs to be cleaned. You’ll only have to do this a few times before the nutrients come down and the algae color lightens up; then you can go back to weekly cleanings.

Q: I’m worried about my screen/pipe clogging and causing an overflow; what can I do?
A: Screens hardly ever clog from debris/junk flowing in the water; they only get sections of “reduced” water flow where the algae grows up into the slot in the pipe. The ways you can prevent this is (1) Install a “light shield” along the length of the pipe; a strip of plastic that blocks light from reaching the top part of the screen near the slot. (2) When cleaning the screen, clean the top 1/2″ (12mm) of the screen extra well, and leave no algae behind. This will cause the algae to take longer than a week to grow into the slot, by which time you will be doing another cleaning. However if you would feel safer with a backup, then just put an “L” on the end of the pipe, pointed up a few inches. If the screen ever somehow got plugged up, the water would just get pushed out and up the “L”, where it would flow down into the sump. And you would hear it.

Q: Will scrubbers work with other filter devices, like skimmers, vodka, reactors, denitrators, poly pads, zeo, etc?
A: Scrubbers will works with any device/setup. One exception, which is not really a filter, might be xenia; if you want to keep your xenia, you’ll probably need to start feeding much much more after you start using a scrubber. If you don’t feed more (much more), the xenia will probably fade away. Also, you cannot use a scrubber with a planted tank; the scrubber will compete with the plants for CO2.

Q: I heard there is someplace you can buy a turf screen already grown.
A: If you need instant results, and you can’t wait a few weeks to grow your own algae, then you can buy pre-grown turf screens from Inland Aquatics in the U.S.

Q: Why do I want to clean my screens with freshwater? Don’t I want to keep as many pods as possible?
A: Don’t worry, you’ll have endless pods. Microscopic pods grow so fast in the algae (by the millions each day), that they start eating the layers of algae underneath. This releases nitrate and phosphate back into the water. Sometimes if the algae is not too thick, the pods will eat big holes in the algae that you’ll see on the screen. This is not good. By cleaning the screen weekly in freshwater in the sink, the pods will be removed, and excess nitrate and phosphate will not be released into the tank. But the next day there will be millions more pods. Enough to feed several mandarins and scooters.

Q: In a typical emergency, like a big fish dying overnight, or a huge amount of food being dumped in that you don’t know about, isn’t it better to have a skimmer than a scrubber?
A: Well, an “emergency” is best handled with everything that you own; Skimmers, scrubbers, and anything else will only help for the next five or ten hours that follow. But since most of us don’t design our tanks with emergencies as the prime focus, we need to choose equipment based on what has the greatest impact by itself. A large dead fish, or a ton of food, doesn’t cause a problem immediately. It’s only hours later when bacteria have started converting them to Ammonia/Ammonium, that you have a problem, since Ammonia/Ammonium are poison in your tank. Ammonia/Ammonium are the favorite food of algae, so if you have a scrubber, the Ammonia/Ammonium is removed as it develops. If you only have a skimmer, however, you are in trouble because a skimmer does not remove any Ammonia/Ammonium at all. None. Not even a little. So in the case of the large dying fish, if you only have a skimmer, then your entire tank will die because there will be nothing to remove the Ammonia/Ammonium. In the case of excess food, the skimmer will indeed remove a lot of it (that’s what skimmers do, remove food), so there will be less food to rot into Ammonia/Ammonium. But the question is, will the Ammonia/Ammonium that remain still be enough to kill things. At least with a scrubber, all the excess food will stay in the water (to be eaten by fish/corals), and the Ammonia/Ammonium that develops will be removed. With excess food, having both a skimmer and scrubber together works the best. But in the case of a dead fish, having both is of no benefit; only the scrubber performs a useful function. All this is assuming, of course, that you are not around to do emergency waterchanges, etc.

Q: I have lots of green hair algae all over my rocks, but my nitrate and phosphate always measure “zero” when I test it. How can this be? Are my tests bad?
A: No, your tests are fine. What you are seeing is the power of algae at removing Inorganic Nitrate and Inorganic Phosphate (which is what test kits read.) You have so much algae in your display that all the nitrate and phosphate is eaten before your test kits can read it. Basically, you already have a scrubber; it’s just in the wrong place… on your rocks.

Q: Is there a screen shape that is the most powerful?
A: Yes. Vertical screens that are very wide, but not very tall, are the most powerful. This is because wider screens use more flow, because they have longer slots, thus processing more water for the same size screen. (Note: Other things have far more effects on performance, such as light, flow, screen roughness, and weekly cleaning.)

Q: I am starting to grow tough turf; what do I do?
A: Turf does not need to be cleaned off the screen as often. But when it is cleaned, a razor blade is usually necessary to scrape it off. Scraping a real turf screen is usually done every two months. However, green hair algae and slime will cover the turf quickly, so you still need to “clean” the turf in your sink with freshwater every 7 days, as normal. Scrub the turf under the water like you are shampooing hair. The green hair and slime will come off, but the turf will remain. This is very quick and easy. Then, every other month, do a full scraping with a razor.

Q: I travel quite a bit, and sometimes I can’t work on my tank for weeks at a time. Can I still use a scrubber?
A: The easy and safe answer, is no. However, depending on how much you want to learn, and how much space and time and electricity you want to devote to your scrubber, it is possible to design and build a very oversize scrubber that will last for an entire month between cleanings. The reason a standard-sized scrubber needs weekly cleanings is because the new algae growth covers up the old growth, causing the old growth to be shaded, which kills it. Weekly cleaning removes the growth before this happens. A very oversized scrubber, however, would only build up a very thin layer of algae across a very large area (same amount of algae, spread over a larger screen). Since this layer would not be thick enough to block the light, it would continue to stay alive until you returned home. The bigger the screen, the longer it can go. The standard screen size of one square inch (6.25 square cm) per U.S. Gallon (3.8 liters) goes one week; so two times area this would go two weeks; three times for three weeks, etc. But the lighting must also be doubled or tripled. You can’t increase the screen size without increasing the lighting across the screen too. Thus you not only have to be able to accommodate the large size, you also have to pay for the increased electricity, every week. At some point, probably around 3 weeks, the problem will then become the pods, which will eat the algae so fast that the filtering will start to drop. The solution for this is a very complex switching device that stops the SW flow, then runs RODI (to kill the pods), and then switches back to SW. Probably not worth it unless you are a master DIY’er.

Q: Should I continue to run mechanical filters after I install a scrubber?
A: Not normally. Mechanical filters such as foam pads, floss and filtersocks trap food and cause it to rot into nitrate and phosphate. Even if you planned on cleaning the filters daily, why feed the tank at all if you are just going to trap the food and remove it? And yes, fish waste is food too, for corals and clean up crews. Other items can also act as mechanical filters, such as carbon and phosphate reactors/canisters, and bio balls. Large food items (like mysis) get stuck in them and rot. Carbon is not needed with a scrubber (unless it’s needed for something else, like removing medication); phosphate-removal is handled by the scrubber, as is the nitrification function of the bio media/balls (and the live rock and sand, if you have them). Basically, food such as mysis should be able to flow throughout your entire system for hours and hours, without getting stuck, so that your fish and corals can eventually eat it. All the rest will be taken care of by the scrubber. One exception might be a large fish-only tank, where you have no need for small food particles floating around at all.

Q: If I want extra filtering, can I just increase the size of my screen?
A: Only if you increase the lighting too. Extra screen does no good if it’s farther than 6 inches (15cm) from the light; 4 inches (10cm) should really be the maximum. Actually, just adding extra light is the best way to increase filtering.

Q: Before building my scrubber, I had a little algae on my rocks. Now that I’m using a scrubber, my test kits don’t measure any more nitrate or phosphate, and my glass and sand stay clean, but now I have MORE algae on certain rocks than I did before. Isn’t the scrubber supposed to remove algae from the rocks too?
A: Absolutely. Matter of fact, what is happening is that the scrubber is removing so much phosphate from your water that the phosphate that was stored in your rocks is starting to leak out. Before, when the phosphate in your water was high, it soaked INTO your rocks like a sponge. Now that the phosphate in your water is low, it’s leaking OUT of the rocks. And when the phosphate leaks out to the surface of the rock, it’s exactly what algae needs to grow there. So anytime your phosphate measures zero, and you only have algae on certain rocks (and none on your sand, glass, or plastic), then you can feel good knowing that the phosphate is being removed from those rocks. After it is removed, the algae will go away. How long this takes depends on how much phosphate was in the rocks, and how powerful your scrubber is. Typically it takes 3 weeks to 3 months.

Q: If I don’t use a skimmer, and I don’t have air bubbles, how will my tank get oxygen?
A: From the scrubber. A scrubber adds oxygen two ways: Air contact, and algae photosynthesis. The air contact works just like a skimmer; the water tumbles across the screen in a thin layer, and absorbs oxygen from the air (this is especially so if you use a fan to blow air across the screen.) Algae photosynthesis works just like trees; they take in C02, and let off oxygen. Algae is so effective at putting oxygen into the water that most times the water gets to be “supersaturated” with oxygen, which is the highest level it can reach. Skimmers never achieve this. Matter of fact, it’s the algae in the ocean, and not the trees, which makes the oxygen that you breath.

Q: After I clean my screen, I get a “spike” in nutrients (nitrate and phosphate) for a day or so until the screen starts to grow again. What can I do to stop this?
A: You can clean half of the screen each time. You still want to take the whole screen to the sink (because it needs fresh water to kill the pods), but only clean the algae off of half of it. The easiest way to do this is to have two smaller screens, and take one of them to the sink every 5 days for cleaning, instead of 7 days. This way, the other screen only has to wait 10 days before it’s cleaning (10 days is about the max time that a screen can go without fresh water to kill the pods.)

Q: I’m building a horizontal type of scrubber, where the water and algae will only be on the top side of the screen. Can’t I use half of the 35 gph per inch recommended flow?
A: No. Since the screen is horizontal, it does not have much gravity pulling the water across it, and thus the flow becomes slow and “thicker” (like a pond). This is in contrast to a vertical screen where the water rushes down faster in a thinner stream (which works best). So to get the speed of the flow higher in a horizontal version, keep the same 35 gph per inch, even though it’s all flowing on just one side.

Q: People on other forums suggested that I “cook” my rocks in order to get the phosphate out of them. Is this cooking still needed if I have a scrubber?
A: No. “Cooking” just pulls out phosphate from the rocks by putting the rocks in low-phosphate water; thus the phosphate “flows” out of the rocks. In non-scrubber tanks, the rocks are in high-phosphate water, and that’s why they accumulated phosphate. When you add a scrubber to a tank, phosphate is removed from the water, and the phosphate then starts coming out of the rocks without having to remove the rocks from the tank. Note: As the phosphate comes out of the rocks, green hair algae will grow MORE on the rocks, especially on sharp corners and on top sections under bright light. It takes a scrubber 3 weeks to 3 months to pull all the phosphate out of the rocks, depending on how powerful the scrubber is, and how much phosphate was in the rocks.

Q: I’m getting very long, thin, green hair algae growing in my scrubber, but it’s so long and thin that’s it’s clogging the drain, and it’s letting go and going into the display. Is this normal?
A: No. This has been reported to happen in the rare case of when there is a lot of nitrite and nitrate, but no phosphate. If this no-phosphate situation is indeed the problem, then adding phosphate will fix it. An easy way to do this is to get some Mono Potassium Phosphate (one source is and dissolve a spoonful of it into a cup of FW. Add a little of the water to your tank, and test for phosphate again. If you have a reef tank, repeat until you start measuring phosphate (0.03ppm would be good). If you have a FOWLR tank, you can add more since you have no coral growth to worry about (0.1ppm would be good). If you have a FW tank, you can add the most, since you want to have as much phosphate as is needed to allow the removal of all ammonia, nitrite and nitrate (1.0 or 2.0ppm phosphate is allowable).

Q: My first scrubber was simple CFL design and worked ok, and my second scrubber is an acrylic type using T5HO bulbs. The first one did not affect alkalinity, but my current seems to cause the alk to drop.
A: When algae can’t get enough CO2 from the water, it then uses alk. Your first scrubber, like most DIY designs, was not strong enough to use up a lot of CO2, but your second one is. Strong scrubbers consume so much nitrate, phosphate etc, that they may need additions of alk to keep up. This is easily done by adding a spoon of Arm & Hammer baking soda (in the yellow box) to the water as needed. The alk will come right up.

Q: Sometimes my scrubber gets yellow places on the screen. Is this ok?
A: It’s not whether it’s ok or not, it’s just not performing as well as it could be. Yellow is caused by lack of iron. When spots on your screen lack flow, the algae can’t get the iron it needs from the water, and so it turns yellow. The usual fix is just to increase flow. Very powerful scrubbers, however, even with lots of flow, will sometimes consume enough iron that there are still yellow spots. The easy solution is to add iron, such as Kent’s Iron + Manganese. Start slowly, per the instructions, and then start adding more each day, until the growth turns all green. Do NOT put large amounts (more than the instructions say) in on the first day, because too much iron will start hurting some corals (especially bubble corals).

Q: I’m getting good scrubber growth, but the nitrate is not coming down. What can I do?
A: Check your phosphate. If it is “zero”, then you might have to add some phosphate in order for the nitrate to start coming down (algae needs both phosphorus and nitrogen to grow). An easy way to do this is to get some Mono Potassium Phosphate (one source is and dissolve a spoonful of it into a cup of FW. Add a little of the water to your tank, and test for phosphate again. If you have a reef tank, repeat until you start measuring phosphate (0.03ppm would be good). If you have a FOWLR tank, you can add more since you have no coral growth to worry about (0.1ppm would be good). If you have a FW tank, you can add the most, since you want to have as much phosphate as is needed to allow the removal of all ammonia, nitrite and nitrate (1.0 or 2.0ppm phosphate is allowable). In all cases, as the nitrate finally starts coming down, the phosphate will start coming down too.


Q: If scrubbers work so well, why haven’t I heard of them before, and why haven’t people been building them before?
A: Because the inventor of the scrubber had a patent on his design, but he did not sell any scrubbers to the public; and he did not allow others to sell them either. So people thought that since his design was the only one that was patented, then it must be the only design that worked. As you can see, his is not the only design that works.

Q: If scrubbers are “so much better than…”, why do so many people use skimmers?
A: Because skimmers companies have money for promotion, which makes it look like skimmers are “everywhere”. Algae has no money for promotion. Also, the number of people using something is not relevant, at all, to how good it is. It’s a trick called “Appeal to Popularity”, otherwise known at Argumentum ad populum…

Q: Besides a scrubber, what other filter choices do I have?
A: These…

Nitrate Removers: Coiled denitrators, vodka, zeo, poly filters, live rock, DSB’s, RDSB’s, water changes.

Phosphate Removers: Vodka, zeo, poly filters, GFO, water changes.

Ammonia Removers: Bio balls, live sand, live rock, poly filters, Prime/AmQuel, DSB’s, RDSB’s, water changes.

Food Removers: Skimmers, filter socks, foam, floss, water changes.

Q: What are the drawbacks to scrubbers?
A: You have to build them; they require weekly cleanings; they give off a lot of light (unless you enclose them); and they cause lots of cooling/evaporation (unless you enclose them). Any other drawback that you may have heard about is either old information (previous to August 2008), or the scrubber in question was built incorrectly or is being run incorrectly, which does happen a lot in DIY designs.

Q: I’ve heard that these “waterfall” type of scrubbers are not real “ATS” dumping scrubbers.
A: “Scrubbers” and “ATS scrubbers” are anything that move water over a lit surface, for the purpose of growing algae. What the “ATS” confusion is related to, is that one of the original patented scrubber designs in the 1980’s used a dumping design that dumps water onto a horizontal screen, and the owner of this patent also owns the trademarked “ATS” name (as well as other scrubber designs). So, people confuse the word “ATS” with that particular dumping design, only because it was the most popular design at that time. But this person also made ATS designs that did not have dumping mechanisms at all.

Q: Can I speed up my scrubber by removing algae from the display?
A: If you physically remove algae from the tank, and throw it away, then yes. But if you just scrub the algae off the rocks and leave it in, or if you just put more snails/crabs/fish in to eat it, then no. Scrubbers grow and filter better in low-nutrient water; low nutrients cause greener hair algae to grow on the screen, which let the scrubber filter better. If you kill the algae in the tank, but don’t pull it out, the nutrients that were in that algae go back into the water. These higher nutrients will cause the scrubber to grow darker algae, which do not filter as good as greener algae. So leave the algae alone in your tank, unless you are going to physically pull it out and throw it away. Basically, the more algae that is in your system, the less nutrients there will be in the water.

Q: Will a scrubber help me to grow coralline?
A: Absolutely. The main reason most tanks don’t grow coralline is because their phosphate levels are too high. Anything over 0.03ppm is going to slow down or stop coralline. Since a scrubber will reduce the phosphate to less than 0.03ppm, it will allow the coralline to flourish, if not take over.

Q: Is it OK to remove the screen everyday to look at it?
A: No. You don’t want to move the screen if you don’t have to. Moving it will increase the chance of algae letting go, and, if you have thick growth that is growing on the bottom of the scrubber container, removing the screen will break some of that algae and put particles into the water. It’s best to wait for your cleanings, when the water is off, to remove the screen.

Q: Can I convert an HOB or canister into a scrubber?
A: It’s never been done. They are just too small.

Q: Some experienced aquarists told me that a scrubber might make the water cloudy or yellow.
A: Cloudiness is caused by not cleaning the screen weekly (which was how they did it in the 1980’s, 1990’s and early 2000’s). When not cleaned, the underlying layers of algae get covered up and shaded by the newer outer layers, and thus the underlying layers die and get washed back into the water, causing cloudiness. Yellowing is caused by cleaning the algae without removing the screen first. You are supposed to remove the screen and clean it in the sink under freshwater. If you clean the screen when it’s still in the system/sump/bucket, the broken algae strands empty into the water, and yellow it. (This fact was discovered by “FLjoe” who is on several reef forums).

Q: I’m keeping my skimmer. When I add a scrubber, should I expect the skimmer to produce less foam?
A: No. Adding a scrubber does not remove any food (protein), and that’s what skimmers remove… food.

Q: After I add my scrubber, how long should I wait before removing other equipment?
A: It’s not how many weeks you wait, but how many screens of algae you wait. Wait until you have cleaned off three full screens before you remove your other filters. This way, you are guaranteed that nutrients are being removed quickly (otherwise the algae would not grow). The very best things to look at, however, are the nutrient tests; they should be going down.

Q: Shouldn’t I make sure my screen has lots of air flowing over it?
A: Only if you want cooling and evaporation. Otherwise, scrubbers do not need air to operate; the CO2 that is removed from the water goes directly into the algae, and the oxygen that the algae releases goes directly into the water. Air is not used in the process.

Q: If I add a scrubber, can I no longer treat my fish-only tank with copper or other treatments to get rid of parasites?
A: You don’t want to use any treatments that directly affect algae, such as AlgaeFix or Algaequel (whether for FW or SW). However, algae eats copper, even though some algae removing products use copper. And some people have used copper for their fish, and it did not affect the algae too much (and then, of course, the algae ate the rest of the copper in a few days.) So, it’s ok to use such treatments. Other treatments that target phosphate, nitrate, ammonia, etc, will not directly hurt a scrubber (other than taking away the scrubber’s food). Chlorine/chloramine treatments should not hurt the scrubber either. But if you need to control parasites such as ick, use an ultraviolet sterilizer (U.V) instead. The ick will be wiped out in a few days, then you can turn the U.V. off. And it’s a permanent fix (just turn it back on when needed).


2 Responses to “Algae Turf Scrubbers – How To Remove Algae”

  1. Bud Says:

    Funny place to find my write-up! Works for all kinds of different applications. This is “Floyd R Turbo” from the reef forums BTW.,, etc etc. I re-vamp the entire “basics” recently, you can find it on the Algae Scrubber website, on that site I also uploaded the text files that you can use to re-post it all anywhere you want. If you want to update this page with that info, by all means do it! Thanks for spreading the message about this system

  2. There's certainly Says:

    Thanks a bunch for your splendid post. I seriously like the blogging site and thought which I’d let you know! :D Cheers, There’s certainly