Mega Powerful Nitrate and Phosphate Remover - DIY!

Part 1 of 2:

Mega Powerful Nitrate and Phosphate Remover - DIY!

Are you tired of green on your rocks? Do you have to clean your glass more than once a week? Well then I'm sure you've been told (or you've figured out) that your Nitrate and/or Phosphate are too high. Sure enough, if these are too high, the green starts growing. Phosphate is the important one: If you can detect any phosphate at all with a hobby test kit (like Salifert), then it's high enough to cause algae to grow. So, what can you do?

Build an algae filter screen, that's what you can do. An algae filter screen, also known as a turf algae filter, a turf scrubber, or an algae scrubber, basically filters the water clean of nitrate and phosphate so that the green on your rocks and glass goes away. It does this by "moving" the growth of the algae from the tank to a "screen" outside of the tank. The idea is that you create a better growing environment on the screen than occurs in the tank, so that the algae grows on the screen instead. It works great!

Here's what you can expect: If you build your algae filter properly, your nitrate and phosphate will be incredibly low, sometimes unmeasureable by hobby test kits, within four weeks. I use Salifert test kits, and the readings I get are "clear" (zero) for both the Nitrate and the Phosphate tests. This is what you want. If you have been trying to get this yourself, then an algae filter is for you.

Here is my Algae Filter in a 5-gallon bucket; it's the only filter I have (other than the live rock) on my 100 gallon reef:

Here is the filter in operation with the lights on:

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Here is my tank:


And here are the only things you need to build a bucket version of this filter:

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My nitrate and phosphate are zero (clear on Salifert test kits), and the only thing in my sump is water. I removed the skimmer, carbon, phosban, polyfilter(s), and filtersock; I don't use ozone, vodka, zeo or anything else. I'm feeding massive amounts too; enough that if I had my previous filtering setup, I'd have to clean the glass twice a day, and everything in the tank would be covered in green or brown algae. Amazing.

The only thing you need to decide on is how big your algae filter screen needs to be, and if you want it to be in your tank's hood, or in a bucket, or in your sump. The basic rule is one square inch of screen for each gallon of tank water, if the screen it lit on both sides; the screen size should be twice this if the screen is lit up on just one side. A 12 X 12 inch screen, lit both sides, = 144 square inches = 144 gal tank; a 7 X 7 inch screen lit both sides = 49 gal tank; a 6 X 6 lit both sides = 36 gal tank. Algae filters get really small as you can see. A 12 gal nano tank needs just 3 X 4 inches! This small thing can replace the skimmer, refugium, phosphate removers, nitrate removers, carbon, filtersocks, and waterchanges, IF THE PURPOSE of these devices is to reduce nitrate and phosphate. If these devices have any other purpose, then they can't be replaced. If your tank is bigger than a 75, then just start with a 5 gallon bucket size and see how it goes. You can always add a second one, or build a bigger one later.

My example bucket version takes about 4 hours to build. Water goes in the pvc pipe at the top, flows down over the screen, then drains out the bottom. That's it! Oh, and it has clip-on lights. I can feed the tank a lot of food, and anything not eaten by the corals or fish eventually ends up as algae on the screen.

Here are some examples of DIY algae filter screens already built, from a simple nano one:

to larger ones:

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Here are some advantages of an algae filter:

o Allows you to feed very high amounts without causing nuisance algae growth in the tank.

o Can replace waterchanges, IF THE PURPOSE of the waterchange is to reduce nitrate or
phosphate or algae growth. Otherwise, it does not replace the water change.

o Grows swarms of copepods.

o Increases pH.

o Increases oxygen.

o Will NOT spread algae into the tank. It removes algae FROM the tank.

o There is no odor from the algae (only a slight ocean smell when cleaning it).

o Is very quiet when flowing, similar to a tabletop decorative waterfall.

o Introduces no microbubbles when adjusted.

o Removes ammonia too.

o You can even make a portable bucket! Just unplug the lights, lift up the pump
out of the tank water, and go put it in your next tank (or your friend's tank).
Don't let the screen dry out though.

o Works in saltwater or freshwater.

Part 2 of 2:

How to build it:

First, get your screen. Any stiff material that has holes in it, like knitting backing, plastic canvas, rug canvas, gutter guard, or tank-divider will do. Try going to hardware stores, craft stores, garden stores, sewing stores, or just get one of these online (in order of preference):
3.75- & 5-mesh Rug Canvas Assortment, 5 Pieces
Aquatic Eco-Systems: Tank Dividers

Don't use window screen though. The main problem with this kind of "soft" screen will be getting it to hold its shape; it will bend and fold too much. Stiff screen is easier to make stay put, and easier to clean.

If you have a nano with a filter hatch on top of the hood, then it's super easy: Just cut a piece of screen to replace the sponge filter, and put it where the sponge filter went. Leave the hatch open, an set a strong light on it, facing down directly on the screen. This is a good bulb to get; it will be bright enough to power the screen, and to light up your nano too:

23 Watt R40 Compact Fluorescent Flood 5100K Full Spectrum CFL

If your nano does not have a filter hatch on top of the hood, or if you have a regular tank, then here are the larger versions:

The first and main thing to consider is the flow to the screen. You need about 35 gph (gallons per hour) for every inch of width of the screen. Thus, a 2" wide screen would need 70 gph, and so on. Here is a chart:

Screen Width-----Gallons Per Hour (GPH)

1" 35
2" 70
3" 105
4" 140
5" 175
6" 210
7" 245
8" 280
9" 315
10" 350
11" 385
12" 420
13" 455
14" 490
15" 525
16" 560
17" 595
18" 630
19" 665
20" 700

Note that it does not matter how tall your screen is, just how wide it is. Let's start with an overflow feed: In this case the amount of flow is pre-determined by how much is overflowing; the maximum flow you'll get to the screen will be what's going through your overflow now. This is easy to figure out by counting how many seconds it takes your overflow to fill a one-gallon jug:

60 seconds = 60 gph
30 seconds = 120 gph
15 seconds = 240 gph
10 seconds = 360 gph
8 seconds = 450 gph
5 seconds = 720 gph

Take this gph number that you end up with, and divide by 35, to get the number of inches wide the screen should be. For example, if your overflow was 240 gph, then divide this by 35 to get 6.8 (or just say 7) inches. So your screen should be 7 inches wide. How tall should it be? As tall as can fit into the area you have, and, as tall as your light bulbs will cover. But how tall it is not as important as how wide it is.

Pump feeds: Since with a pump you have control over the flow, start with the size screen you can fit into your space. If the screen will go into your sump, then measure how wide that screen will be. If the screen will go into a bucket, then measure how wide that screen will be. Take the width you get, and multiply by 35 to get the gph you need. For example if you can fit a 10 inch wide screen into your sump or bucket, then multiply 10 by 35 to get 350 gph. Thus your pumps needs to deliver 350 gph to the screen.

You can construct your setup using any method you like. The only difficult part is the "waterfall pipe", which must have a slot cut lengthwise into it where the screen goes into it. Don't cut the slot too wide; just start with 1/8", and you can increase it later if you need to, based on the flow you get. I used a Dremel moto-tool with a "cut off wheel":

Now install the pipe onto the screen/bucket by tilting the pipe and starting at one side, then lowering the pipe over the rest. You may have to wiggle the screen in some places to get it to fit in:

Lighting: This is the most important aspect of the whole thing. You must, must, have strong lighting. I'll list again the bulb I listed above:

23 Watt R40 Compact Fluorescent Flood 5100K Full Spectrum CFL

... This the minimum you should have on BOTH sides of your screen. You can get even higher power CFL bulbs, or use multiple bulbs per side, for screens larger than 12 X 12 inches, or for tanks with higher waste loads. The higher the power of the lighting on the screen, the more nitrate and phosphate will be pulled out of the tank, and faster too.


Regardless of which version you build, the startup process is the same. First, clean the screen with running tap water (no soap) while scrubbing it with something abrasive. Then dry it off and sand it with sandpaper on both sides. Then get some algae (any type) from your system and rub it HARD into the screen on both sides, as deep and as hard as you can. Then run tap water over the screen to remove the loose algae pieces; you won't see the spores that stick... they are too small, but they are there. Don't forget this algae rubbing part... it will speed up the start of your screen by a few days. Install the screen and turn on the water.

You can leave the light on for 24 hours for the first week if you want to speed up the process; otherwise just put it on a timer for 18 hours ON, and 6 hours OFF. You will see absolutely nothing grow for the first two days. On day 3 you'll start seeing some growth, and by day 5 most of the screen should have a light brown coating. If this level of growth does not happen on your screen, your lighting is probably not strong enough, or it's not close enough to the screen. Increase the bulb power, or move it closer.

When the screen looks something like this:

...then you want to give it it's first cleaning, on ONE SIDE only. Take the screen to the sink, run tap water on it, and just push the algae off with your fingers (not fingernails):

Wait a week, and clean the other side, gently. Wait another week and clean the first side again, etc. After a while you'll have to press harder to get the tougher algae off, and after a few months you'll probably need to scrape it with something, and it may eventually get so strong that you'll need a razor blade to scrape it off. But for now, be gentle; you always want some algae to remain on the screen when you are done. NEVER clean it off completely.

Don't forget to test your Nitrate and Phosphate before you start your filter, and each day after. I use Salifert:

Salifert Test Kits

Post your pics of how you build it, the growth day by day, and your nitrate and phosphate readings, so we can all see how you are doing!

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Elite Fish
Nov 1, 2005
Jacksonville, FL
Welcome to the tank! And one hell of a way for you to make an introduction. This screen idea seems pretty damn sweet. I may have to give this a try. I think I would go with a unit above my tank boxed off in a cabinet.

You did an excellent job on putting this together.

Just got a couple questions for you.

ok lil more than a couple.

How does this help you feed more? Every tank has DOC (dissolved organic compounds). They are the end result of your foods you feed the tank and any critter that may have passed and disappeared. I don't understand how algae can remove these. Leaving them in will mess with your PH, as they dissolve they create a form of acid in the tank negating the waters buffering ability. You can add more buffers, but doing so is going to increase the hardness of your water until eventually your going to end up with liquid rock, literally. Your going to fossilize your fish 2 million years early. j/k

How does it help your PH? Using up nutrients like nitrate and phosphate doesn't account for the real reason for PH drops, the DOCs.

Skimmers are one of the only ways to remove DOCs. Since they are dissolved a standard filter won't touch them.

I appreciate your input on this. I'm very curiouse..heck I might start building this next week.

Thanks, good to be here. Was fun to discover and make this (it saved my tank), and watch others build them too.

How does this help you feed more
Because you are not limited by nutrient build up, i.e., causing nuisance algae to start growing in your display.

How does it help your PH
Algae absorb CO2, and release O2. Just like trees.

Every tank has DOC (dissolved organic compounds). They are the end result of your foods you feed the tank and any critter that may have passed and disappeared. I don't understand how algae can remove these
Algae doesn't; bacteria does. Just like in the ocean. Here are some interesting technical points taken out of the current issues of Advanced Aquarist:

Advanced Aquarist's Online Magazine - Feature Article: Total Organic Carbon (TOC) and the Reef Aquarium: an Initial Survey, Part I
Advanced Aquarist's Online Magazine - Feature Article: Total Organic Carbon (TOC) and the Reef Aquarium: an Initial Survey, Part II

"Greater than 97% of the organic matter in the oceans is in the form of DOC"

"The majority of the DOC in the oceans is consumed over a time span on the order of hours-to-weeks."

"The generally accepted value of deep ocean TOC (DOC in this instance) ranges from 0.45 - 0.60 ppm, a number that appears to be insensitive to collection location. On reefs, however, the DOC (and TOC) value is considerably higher. Even with this point noted, the values of DOC on reefs from the South Pacific to Japan to the Caribbean to the Red Sea are remarkably consistent in their range: 0.7 - 1.6 ppm"

"Bacteria are a critical component in the food web of the reef, as they occupy the role of 'middle man' in the transfer of energy from the source (sunlight) to the consumers on the reef"

"sponges are some of the most prolific repositories of marine bacteria. In fact, some sponges have been studied as effective bioremediation agents in marine aquaculture as a consequence of their exceptional ability to absorb TOC"

"Where does the DOC go ... studies suggest that it is rapidly consumed by bacteria that live in and on the coral itself and not by bacteria present in the water column. Shutting down these endogenous bacteria by antibiotic treatment abolished DOC uptake."

"In total, these data unequivocally demonstrate that the [skimmer] is not required to deplete the aquarium water of TOC. Apparently, naturally biological processes are sufficient in and of themselves to return the post-feeding TOC levels to their pre-feeding values after about 4 hrs or so ... Clearly the skimmer is doing something, given the copious residue accumulated in the collection cup at the end of the week. Perhaps, however, the residue removed by the skimmer is only a rather small, even inconsequential, portion of the entire TOC load that develops in the aquarium water over the course of a week."


Elite Fish
Nov 1, 2005
Jacksonville, FL
Clearly the skimmer is doing something, given the copious residue accumulated in the collection cup at the end of the week. Perhaps, however, the residue removed by the skimmer is only a rather small, even inconsequential, portion of the entire TOC load that develops in the aquarium water over the course of a week."
It's too late for that much reading LOL..I'll take your word on it n read it in the morn. So basically there is a bacteria that will consume the DOC? If that's the case then yeah you don't need a skimmer. And if it works as well as was quoted it will outperform most Skimmers.


Yeah I'm gonna have to give this a try.



Small Fish
Jul 28, 2008
wow... very nice write up..... concidering how expensive refugiums and skimmers are, this is definently something anyone should try out.... i see maybe $100-150 worth of matierials (dont know how expensive the bulbs are)... i have fish only tanks, but still, for how little is invested in it, i might have to try one of these out and see how well it works

thanks for the write up

Pure: Skimmers have their purpose, but removing DOC or Inorganic Nitrate or Phosphate is not one of them. Now I will use a skimmer on my upcoming FO eel tank with no rock and no sand, because I'll have no need for planton floating around. Also, if your livestock has any real chance of spawning and killing everying while you are away, a skimmer helps there too. But for keeping the corals in a reef tank fed with plankton, while keeping nitrate and phosphate at zero, scrubbers can't be beat.

vipers: I could build mine with brand new parts for $60 including bulbs. See the link for the bulbs in the first post. Of course it's nice when you already have most of the parts :) If you have nitrate or phospate or nuisance algae problems in your FO tanks, then yes this will fix it. Also if you make the bucket version, you can move it from tank to tank and filter each one using only one bucket.

dang, this could be huge. really, this is good. the only think i would do is KEEP all the other stuff in there and see if it makes a diiference on if your skimmate is less, your filter socks are cleaner, etc.... but very good idea. I want to install one for my overflow line to the sump.

Today's N-and-P-lowering successes are both from the UR site, and both of them were a build-of-the-day that I previously posted:

"Col" says: "Test results from tonight are N=7.5 & P=0.1 I've not had test results as low as this before. The lighting on side 2 of the screen is really making a difference. Thanks SantaMonica for all your help!

"johnt" says: "Tested today and nitrate has come down from 50 to less than 25:



* = Started Scrubber

"First a big drop in Phosphate and now an equally impressive drop in Nitrate"

Can't be submerged; won't work at all.

It can be horizontal, but it becomes harder to keep rapid flow across the whole screen (since the water will want to stop). It's critical to have rapid turbulent flow. One way might be to dump your entire overflow on a horizontal screen, maybe with a deflector plate in very middle which would cause the flow to spread out sideways in all directions across the screen.

If vertical height is limited, try a short wide screen:


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Large Fish
Feb 25, 2007
Mesa, AZ
I'm thinking about doing this too. It looks like you used one of those aquarium divider screens? My sump pump is way to big for my overflow so I'm going to have to divert some flow back into the sump might be perfect to use that diverted flow for this purpose.

I have an idea. This is for people with the FULL overflows, not the HOB or crazy DIY's like mine. Could you shape it to where it runs along the perimeter of the top of the overflow onthe INSIDE, but BENEATH the teeth, so it runs down on it before going through the bulkhead and whatnot. I think this could be helpful for the people with limited sump space but an overflow with some real estate. You could even use your tank lighting if possible to fuel it.

BUT..... this might cause problems, such as chunks of algae going into the piping that the teeth were originally designed for.

Im just thinking f better places to put it. How about on the last baffle in the sump where its like a little waterfall, just place a screen on there. But lighting would be a problem.

quad: A diverted return pump flow is good; make it adustable. As for screens:

Just get any stiff material that has holes in it, like knitting backing, gutter guard, or tank-divider. Try going to hardware stores, craft stores, garden stores, sewing stores, or just get one of these online:

This "plastic canvas" one might be easier to get into the slot after cleaning, and the edges will not wear; it also will hold it's shape so that a solid frame is not needed:
Everything Plastic Canvas - Plastic Canvas 7 Mesh 12" x 18"

This "rug canvas" is made from fiber so that algae sticks to it the best; but it does not hold its shape when wet, so it will need a solid frame. Also, the edges will wear, so the frame will have to hold the edges down:
No-Slip Rug Canvas 24" x30"

This "tank divider" is mentioned here because you can get them in any LFS, and because they come with clip-on edges that are great frames for any screen. However the screen material itself is very thin and smooth (needs sanding) with not many holes, thus during cleaning it's hard to get algae to stay on the screen:
Aquatic Eco-Systems: Tank Dividers

Overall the rug canvas is the best but takes the most work; the tank divider is the easiest but works least well. I think the plastic canvas is best for most people. Many people ask about using the fiberglass screen from their windows (never use metal!). The main problem of this kind of "soft" screen will be getting it into the slot in the waterfall pipe; it will bend and fold too much. One way around this is to loop it around the waterfall pipe and attach it to itself, instead of slipping it into a slot. In this case you don't need a slot; a series of holes will work. This screen door method is only a last resort though, and will not work that well.

jump: Some people have tried or are doing that now. It's a last resort, and I think there is always room for a real setup if you look at all the option. But if you did it, lighting would be the issue; it has to be directly on it, and not far away. Give it a try.