Mega Powerful Nitrate and Phosphate Remover - DIY!

So with this new version, can I ask a stupid question? If I have a rock in my refugium that grows algae and I don't have snails in there to eat it so it keeps growing, would it do the same thing? I could scrub off the rock once a week.
Light brown is because the screen is too big. There are not enough nutrients in the water to grow thick green algae across the whole screen.

You could try cutting the screen in half vertically, and taping up the slot. But all the light needs to be reflected onto the screen.

Or just see how it goes.
I am considering running an algae scrubber on my 50g cube, I've got a lot of cyano on gha, as well as other nuisance algae. I want to run one, but does this mean I have to remove my skimmer and filter socks?
Jake, if you find the source of your algae (Flow, nitrates, Phosphates) and fix that/those issues the problem will solve itself. You shouldn't need to run one, unless it is something you want to run in place of a skimmer.
I've got 1500gph of flow, I was thinking of running in place of the skimmer, it's gotta be my N/P. I think it might be worth a shot to do this, until I can get a better skimmer. But it's a lot of work. I'm gonna test today. And figure out what's going on
Find the source of your excess N/P. That will fix the problem. Too many people look at these things as an easy way out of being up on tank husbandry. Look into what and how often you feed. Your lighting, bulbs in specific. Go down the line from there.
Also, you may have enough flow, but not enough in some areas. Try adjusting your power heads to get flow into the area where you are seeing cyano.
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Phosphate flow out of rocks

Many people, when they get their scrubber running for the first time, get worried when more (not less) algae starts to grow on their rocks. It seems really strange, especially when nitrate and phosphate have gone lower than before. What is happening is that phosphate is coming out of the rocks. Remember, phosphate is invisible, so you can only see the effects of it, and it always "flows" from higher concentrations to lower concentrations (just like heat does).

Example: If your room is warm, and you put a cold object on the floor, heat from the air in the room will "flow" into the object until the object and the air are the same temperature. Example 2: If you put a hot object on the floor, heat will "flow" out of the object and go into the air in the room, again, until the air and the object are the same temperature. Now suppose you open your windows (in the winter). The warm air in your room will go out the windows, and it will get colder in the room. The object on the floor is now warmer than the air, so heat will flow out of the object and into the air, and then out the window.

Think of phosphate as the heat, and your rocks as the object, and your windows as the scrubber. As the scrubber pulls phosphate out of the water, the phosphate level in the water drops. Now, since the phosphate level in the water is lower than the phosphate level in the rocks, phosphate flows from the rocks into the water, and then from the water into the scrubber. This continues until the phosphate levels in the rocks and water are level again. And remember, you can't see this invisible flow.

This flow causes an interesting thing to happen. As the phosphate comes out of the rocks, it then becomes available to feed algae as soon as the phosphate reaches the surface of the rocks where there is light. So, since the surface of the rocks is rough and has light, it starts growing MORE algae there (not less) as the phosphate comes out of the rocks. This is a pretty amazing thing to see for the first time, because if you did not know what was happening you would probably think that the algae in the scrubber was leaking out and attaching to your rocks. Here are the signs of phosphate coming out of the rocks:

1. The rocks are older, and have slowly developed algae problems in the past year.

2. The scrubber is new, maybe only a few months old, and has recently started to grow well.

3. Nitrate and phosphate measurements in the water are low, usually the lowest they have been in a long time.

4. Green hair algae (not brown) on the rocks has increased in certain spots, usually on corners and protrusions at the top.

5. The glass has not needed cleaning as much.

Since skimmers, filter socks, etc don't remove any nitrate and phosphate, and waterchanges and macro's in a fuge don't remove much, most people have never seen the effects of large amounts of phosphate coming out of the rocks quickly. But sure enough, it does. How long does it continue? For 2 months to a year, depending on how much phosphate is in the rocks, how strong your scrubber is, and how many other phosphate-removing filters you have (GFO, carbon dosing, etc). But one day you will see patches of white rock that were covered in green hair the day before; this is a sure sign that the algae are losing their phosphate supply from the rocks and can no longer hold on. Now it's just a matter of days before the rocks are clear.
I have a question about building an algae scrubber please. Would a black aluminum based wire mesh screen (like for windows) work OK for this purpose? Not sure how aluminum would react with salt water. I'd also like to know where to buy turf screen or something made of plastic if possible. I have a large 200+ gal RR tank but my nitrates and phosphates are high now and I cannot determine the source. I've reduced my feeding, I have a large skimmer and sump, calcium reactor, bio pellets in a separate reactor (to hopefully reduce phosphates/nitrates) and a large eheim canister filter with carbon and de-nitrate rocks/media. I feel like I have a mad scientist lab with all the wires, pumps, reactors, etc and I'm very disappointed with the results. I also have a 5 stage RODI filter and mix with Seachem Salinity salt with 40 gal water changes every month (approx.).

Fish are doing OK but my corals look terrible .. nems are shriveled to almost nothing .. green star polyps died .. leather coral is dying .. etc.

I may try to build an algae scrubber next to help remove phosphates (maybe in my rock?) and see if this helps.

Any suggestion will be greatly appreciated.

Shane D.
You don't want to use aluminum in your tank. The salt water will eat away at it. Are you testing for phosphates? (Also I'd ditch the canister filter... they're notorious for breeding nitrates)
Pics of your sump would help.

Yea you don't want aluminum. Use plastic canvas #7 mesh from the bay or from

As for the source of the N and P:

What do all algae (and cyano too) need to survive? Nutrients. What are nutrients? Ammonia/ammonium, nitrite, nitrate, phosphate and urea are the major ones. Which ones cause most of the algae in your tank? These same ones. Why can't you just remove these nutrients and eliminate all the algae in your tank? Because these nutrients are the result of the animals you keep.

So how do your animals "make" these nutrients? Well a large part the nutrients come from pee (urea). Pee is very high in urea and ammonia, and these are a favorite food of algae and some bacteria. This is why your glass will always need cleaning; because the pee hits the glass before anything else, and algae on the glass consume the ammonia and urea immediately (using photosynthesis) and grow more. In the ocean and lakes, phytoplankton consume the ammonia and urea in open water, and seaweed consume it in shallow areas, but in a tank you don't have enough space or water volume for this, and, your other filters or animals often remove or kill the phytoplankton or seaweed anyway. So, the nutrients stay in your tank.

Then the ammonia/ammonium hits your rocks, and the periphyton on them consumes more ammonia and urea. Periphyton is both algae and animals, and is the reason your rocks change color after a few weeks. Then the ammonia goes inside the rock, or hits your sand, and bacteria there convert it into nitrite and nitrate. However, the nutrients are still in your tank.

Also let's not forget phosphate, which comes from solid organic food particles. When these particles are eaten by microbes and clean up crew, the organic phosphorus in them is converted into phosphate. However, the nutrients are still in your tank.

So whenever you have algae "problems", you simply have not exported enough nutrients compared to how much you have been feeding (note: live rock can absorb phosphate for up to a year, making it seem like there was never a problem. Then, there is a problem).

So just increase your nutrient exports. You could also reduce feeding, and this has the same effect, but it's certainly not fun when you want to feed your animals :)

Skimmers don't remove nutrients; only food particles. Pellets should help, but reduce pH and can harm corals. Canister is only hurting. De-nitrate should help. Waterchanges only remove a small part, and only that day.

Yes you probably have rocks full of P.

Here are some size guidelines:

Scrubbers are sized according to feeding. Nutrients "in" (feeding) must equal nutrients "out" (scrubber growth), no matter how many gallons or liters you have. So...

An example VERTICAL upflow or 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), or
1/2 frozen cube per day (1-sided screen), or
10 pinches of flake food per day (2-sided screen), or
5 pinches of flake food per day (1-sided screen), or
10 square inches (60 sq cm) of nori per day (2-sided screen), or
5 square inches (30 sq cm) of nori per day (1-sided screen), or
0.1 dry ounce (2.8 grams) of pellet food per day (2-sided screen), or
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 1/2. 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.

FLOATING SURFACE SCRUBBERS WITH RIBBONS: Screen size is the size of the box (Lenth X Width), and is 2-sided because the ribbons grow in 3D.

LEDs: Use half the wattage as above. 660nm (red) is best. You can mix in a little 450nm (blue) if you want.

Very rough screen made of roughed-up-like-a-cactus plastic canvas, unless floating surface, which would use gravel and strings instead.

Clean algae:

Every 7 to 21 days, or
When it's black, or
When it fills up, or
When algae lets go, or
When nutrients start to rise