(Note: This is an updated and simplified version of my threads elsewhere on the web. I'm posting here for those people that don't yet know about the topic.)
If you are tired of algae on your rocks, and if you have to clean your glass more than once a week, 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 they are too high, the green stuff starts growing. Phosphate is the important one: If you can detect any phosphate at all with a hobby test kit (like Salifert, etc), then it's high enough to cause algae to grow. So, what can you do?
Build an Algae Scrubber! As of July 2009, thousands of people have built scrubbers for their tanks (and hundreds of them have posted on my other threads), and all have achieved reduced nuisance algae. Many of them have wiped it out completely.
An algae scrubber, also known as a turf algae filter, a turf scrubber, an algae filter, or an algae turf scrubber (ATS) [(c) Walter Adey], basically filters your 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 is my display, January 2009, running on just an algae scrubber:
My scrubber (the black thing sitting on the sump) is made out of acrylic, but most people build simple ones like I show below. Here's what you can expect: If you build your algae scrubber properly, your nitrate and phosphate will be incredibly low, sometimes unmeasureable by hobby test kits, within eight 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 with yours too. If you have been trying to obtain zero reading like this, then an algae scrubber is for you.
My nitrate and phosphate are zero (clear, on Salifert test kits), and the only thing in my sump is water and the scrubber. 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. And it's not just my tank; over the last year, thousands of people have built their own versions of an algae scrubber, and every one has gotten reduced nitrate and phosphate readings, and many of them have completely wiped out all nuisance algae, right down to the bare rock, sand and glass.
The only thing you need to decide on, is how big your scrubber screen needs to be, and how you will pump water through it. 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 as big if the screen is lit on just one side. A 10 X 10 inch screen, lit on both sides, = 100 square inches = 100 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 scrubbers get really small as you can see. A 12 gal nano tank needs just 3 X 4 inches if lit both sides, or 3 X 8 inches if lit on one side. This small thing can replace the skimmer, refugium, phosphate removers, nitrate removers, filtersocks, and waterchanges, IF THE PURPOSE of these devices is to reduce nitrate, phosphate and nuisance algae. If these devices have any other purpose (like growing pods, or removing food), then they can't be replaced.
Here are some examples of DIY algae scrubbers, from a simple nano one with combined light for tank and scrubber:
to larger ones:
Here are some advantages of an algae scrubber:
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 nuisance algae. Otherwise, it does NOT replace the water changes.
o Grows swarms of baby copepods (white specks that crawl on the glass).
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. Your pumps are louder.
o Introduces no microbubbles when built properly.
o Removes ammonia, nitrite, and metals too.
o Works in saltwater, freshwater, and ponds.
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, etc. Try going to hardware stores, craft stores, garden stores, sewing stores, or just get one of these online:
Don't use glass or acrylic; algae can't stick to them. And don't use window screen; sometimes it has an algaecide on it. Whatever other material you use, it's best to use two layers of the material (helps algae stick better). Next you need to "rough up" the screen so algae will stick even better. Use a wire brush, 30 grit sandpaper, a very rough file, or (best) a hole-saw without the drill, to "scrape up" the screen so much that it will almost cut you if you rub your hand over it. What you end up with should look more like a cactus that a piece of plastic.
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, and set a strong light on it, facing down directly on the screen.
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 options for larger versions:
The first and main thing to consider is the flow to the screen. You need about 35 gph (U.S. gallons per hour) (133 lph) for every inch (2.5cm) of width of the screen. Thus, a 2" wide screen would need 70 gph, and so on. Here is a chart:
Note that for flow, 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 already 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:
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? Tall enough for it to stick into the water below (this will keep it quiet). But for flow, 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 pump 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" (3mm) for a single layer of screen, or 3/16" (5mm) for two layers of screen, 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":
Some people don't know how to cut a slot, so they drill holes instead. This not a good idea, and is only a very last resort. You need to have a lot of holes to equal the flow of a slot, and most times the holes end up spraying water sideways. Also, holes are almost impossible to clean the insides. So get help if you need to, in order to cut a slot properly.
Now install the pipe onto the screen 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. Start with something like this:
This 23W CFL bulb is the MINIMUM wattage you should have on EACH side of your screen, unless your screen is smaller than 8 X 8 inches. 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 nutrient problems. The higher the power of the lighting on the screen, the more nitrate and phosphate will be pulled out of the tank, and the faster it will happen. You (almost) cannot have too much light. When some folks report back that their algae scrubber is not growing algae or working well, the problem is ALWAYS that they used weak lights, or the lights were more than 4" away. Every single time.
Regardless of which version you build, the startup process is the same. Put a timer on the light, 18 hours ON, 6 hours OFF. You will see absolutely nothing grow on the screen for the first two days. But on day 3 you'll start seeing some light brown 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 not strong enough (you used a weaker bulb), or it's not close enough to the screen (needs to be no more than 4" from the middle of the screen). Increase the bulb power, or move it closer.
When the screen looks something like this:
...then you want to give it a first cleaning. 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 (yes, 7 days) and clean it again. 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 stiff, 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. Algae has to remain on the screen to do the filtering. Also, NEVER wait more than 7 days between cleanings.
Don't forget to test your Nitrate and Phosphate before you start your filter, and each day after. I use Salifert:
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! There is a lot of info that I did not include here (in order to keep this short), and I've been asked every possible question there is. So if you have an unusual situation, or you think you have thought of something "new", then post it :)
Note about skimmers: Scrubbers do not replace the function of skimmers, just the end result; (they both do different things). Scrubbers remove Nitrate and Phosphate, but leave food in the water for the corals and small fish to eat. Skimmers remove food, but leave Nitrate and Phosphate in the water. If you use both, you will be removing food, Nitrate, and Phosphate.
Note 2: Skimmers do not remove Inorganic Nitrate and Inorganic Phosphate, at all. They remove Organic Nitrate and Organic Phosphate, which is what food is.
Re: Mega Powerful Nitrate and Phosphate Remover
Update: Screens that are too small
This is an example of why a too-small screen can cause problems. The algae gets thick too quick, and the bottom layers die and go back into the water, causing cloudiness and lack of filtering. If you must use a too-small screen, clean it every 3 days instead of 7.... http://www.radio-media.com/fish/SmallScreens.jpg
1. The light is very near the screen, and is not blocked by anything. 2. The flow is very rapid, which transports more nutrients to and from the algae. 3. The flow (on a vertical waterfall) is very thin, which breaks up boundary layer, and which lets the most light through. 4. 7-day cleanings keeps the bottom layers of algae from being shaded and dying. 5. Using FW to clean, kills the pods that normally destroy the algae.
Seeding a new screen is no longer recommended, because (1) you get good growth in a week anyway, and (2) the seeding just washes off and adds nutrients to the water.
Long vacations: Some people want to use a scrubber, but are gone two or three weeks at a time. Here are the options: The easiest is to do nothing. In this case, after three weeks, the underlying layers of algae will have died. When you return, the water may be cloudy and colored, and the nitrate and phosphate may be increased, but after a screen cleaning and some carbon, it will be back to normal in a few days. This option is ok if you leave only once or twice a year. Nothing should be harmed, however. The next option is to remove the screen. For very long trips, and for cases where you have lots of LR and DSB, this might be best. Of course your tank may develop nuisance algae during the trip because of lack of filtering, and you'll have to start the screen from scratch when you return.
Re: Mega Powerful Nitrate and Phosphate Remover
Awards: It's finally happened... A scrubber-only tank (no skimmer) has won Tank Of The Month. "Mudshark", whose pics have been posted here for a while, just won the August Tank Of The Month at MASA site.
RC: They have done a few things to keep people from finding out about scrubbers. They've made it so that when you try to post "algaescrubber.net", it is changed to "clay-boa.com". Also, if you try to search for anything scrubber related there, it seems to always have an "error".
This boundary layer area of the water has zero flow, because it has to have the same flow as the algae, which of course is zero. Since there is no flow (velocity) here, nutrient transport through it is slow. The faster the water flow, the smaller the boundary layer, and the faster the nutrients can get to/from the algae from the water.
One point to clarify about nutrient exchange: Contact with air is not needed. Scrubbers operate the same whether they are sealed or open (except for cooling/evap), because the exchange is not with the air; it's with the water. The reason algae grows better in an overflow, or where water hits a scrubber screen, or where waves hit the beach, is because the flow is higher here and thus the water's boundary layer is thinner, which allows for better nutrient transfer between the algae and the water. This is what a vertical waterfall scrubber tries to achieve: Fast flow from top to bottom. Further info can be found here:
Seagrasses: Biology, Ecology, and Conservation, p 199, by AWD Larkum, Robert Joseph Orth, Carlos M. Duarte:
"As water flows through seagrass [or algae] beds, a boundary layer develops on the sediment surface, as well as on each seagrass [and algae] component exposed to the moving water. The faster the water moves, the thinner the diffusive boundary layer (DBL) becomes, and consequently, the faster the transfer of molecules from the water column to the sediment and/or seagrass [or algae]. It follows then that when currents [flow] are weak, the flux of molecules to the seagrass [or algae] surface may be limited by diffusion through the [boundary layer] (i.e., physical limitation). Under those conditions, many biological sites or enzymes in the seagrass [or algae] tissue are available to assimilate molecules when/if [!] they reach the plant's [or algal] surface.
Re: Mega Powerful Nitrate and Phosphate Remover
1. Change CFL or T5 bulbs every THREE MONTHS!
2. Wattage recommendation: 0.5 Watts per gallon for medium filtering. 1.0 for high filtering.
3. CFL bulbs: 55W is the max that works good. If you need more watts, get two or three smaller ones, or go to T5HO (best)
4. Skimmer overflow: Be careful of your skimmer overflowing (if it does not have an overflow tube.) The rotting food in the skimmer cups has been growing bacteria, and thus producing ammonia, so if it overflows into your sump, the ammonia can kill things. If this happens, then a scrubber removes this ammonia from the water (skimmers do not remove ammonia; they only make ammonia in the cup.)
6. Surges are not recommended for scrubbers, because (1) the have not shown to improve operations, (2) they are hard to diy, (2) they are noisy/messy, and (4) they reduce the filtering contact time with the water.
7. Cleaning: If your screen goes up into the pipe, you can clean the screen extra good in that area, so that less algae will grow up into the pipe.
8. Purple growth: If your screen is new, and you are getting thin purple growth in spots, it is probably cyano because of weak lighting. If your screen is 3 months old or more, and you start getting purple growth, feel it. If it's is furry, then it's turf. If it's not furry, then it cyano.
9. Never run the lighting 24/7.
10. Cyano in display: Sometimes, after an algae scrubber has removed most of the nuisance algae in a tank, cyano will grow a bit more. This is normal, because cyano does not eat the same thing that nuisance algae does (thus, the cyano now has less competition). But the cyano will reduce too eventually. The cyano occurs because it has the capability of getting nitrogen directly from the water, without needing Nitrate, Nitrate or Ammonia/Ammonium (which is what algae gets nitrogen from). But as the scrubber continues to filter, the cyano will have a harder and harder time holding on.
11. Why "polished" water is bad: The "clean" water look you get with a skimmer and other mechanical filters is because the food (i.e, waste "protein") has been removed from the water. This is what you want if you have just large fish. But if you want a "real" natural reef, you don't want to do this. Go diving some time and look at the water on a natural reef; there are millions of specks and dots and particles and things floating in the water in a super thick soup. And that's just six inches in front of your face. These things are what feed everything, including small fish.
Re: Mega Powerful Nitrate and Phosphate Remover
Jason1 on the RS site: "I have to tell you, this thing works great. My tank is definitely showing signs of improvement and looks really cleaned up from what it used to. Thank you."
Danno.Thomas on the SWF site: "Have mine up and functional on a 30 gal, that was just changed over from a 20 gal, had zero new algae growth in the DT. Scrubber is working like magic. Small feather dusters abundant. 6 years in the hobby and my tank has never looked more alive. This is my exclusive filtration."
Troythegreat on the 3R site: "i personally think that scrubbers are a Godsend to reefers. IMO scrubbers work much better than skimmers at 1/10th the cost, all you need is a little discipline. I've had my scrubber running on my 75gal for about 7 months without any trace of nitrates or phosphates. I have 2 clowns, 4 damsels and a engineer goby plus many coral. i feed my coral once a day and my fish twice a day.........i clean the scrubber every 5 days and change carbon once a month."
Chadjwil on the scrubber site: "I've been running an algae scrubber on my 55 [for 7 months]. That tank has never had a skimmer or canister or any other filtration in it, ATS since birth! I'm totally loving it, and...due to space restrictions in the stand ... my screen is undersized, and until last week it was under-lit (bare minimum now), and it's still keeping that tank clean and nutrient free. My fish are so healthy looking, more so than all but the best of the LFS within 50 miles, and my shrimpies molt like mad. I used to be a little leary about telling people that I ran an ATS because of all the sideways looks and comments that I got (and I'm sure my wife thought I was crazy too), but over the last few months more and more people have been commenting on how nice our tank looks, and that theirs was full of algae and a pain to clean all the time, we must spend all our time cleaning and screwing with it...now I get a lot of satisfaction telling them that I spend 5 minutes scraping algae off a plastic tank divider every week or so and I'm done. True believer here."
Re: Mega Powerful Nitrate and Phosphate Remover
Update: Deep-Sump Nano's
There are two types of nano's: The one that has a hatch on the top, so you don't have to open the whole lid to get to the filters, and the one without a hatch, where you do have to open the lid. It's this second one (with a deep "sump"), that is the most difficult to put a scrubber into. Indeed, if at all possible, you want to instead make an external scrubber, that sits above the tank:
You can enclose the scrubber with a box, or just use the lid of the bucket, to keep the light in. And actually, since nano's need such small screens, you could just use a coffee can, with the lid, which will block out all light once sealed. Decorate the can like a vase, and it will add to your decor. And use black tubing too so it looks nice. It doesn't need air flow, unless you want evaporation and cooling. Regardless, if you do this design, make sure to use "aquarium-safe" silicon on all electrical connection inside the bucket (including where the bulb screws in), because water and salt will build and short it out.
If, however, there is no possible way to put a scrubber above your nano, then you can install one in the "sump" area if you are good at DIY. It's a tight fit, but it can be done:
The idea is to use one of the compartments (probably the middle one) for a waterfall area. For lighting, although Riaanp put the light inside, it's probably best to put the light on the outside (back) of the tank, and scrub off the paint on the backside so that the light can get through to the scrubber screen. The bulb only needs to be one watt for every gallon, so a 13 or 18 watts CFL 3000K is fine.
Fortunately you don't need much screen size for a nano... just 2 square inches (6.25 square cm) for every U.S. gallon (3.8 liters), because the screen is one-sided.
This type of setup is nice because it does not require any cutting of the sump walls, and thus can be converted back easily. Also, there is no real cost... just the screen (2 layers of roughed-up plastic canvas, about $1 USD), and the bulb and socket, probably $7.
Re: Mega Powerful Nitrate and Phosphate Remover
Nano scrubbers: In my last update, I said a coffee can would make a good nano scrubber. I meant a plastic coffee can.
Wattage: Your goal should be to get at least 0.5 watts of CFL (compact flourescent light) for each gallon of water, for medium filtering. For high filtering, get 1.0 watts per gallon. And don't use incadescent bulbs... they are much too hot and use too much power. The biggest CFL bulbs you should use should be 45W. If you need more, use extra bulbs, not a bigger bulb.
Be sure not to run bulbs 24 hours.
Be careful of overflowing skimmers; there is a lot of ammonia in that skimmate. A scrubber will help eat that ammonia if it overflows.
If you have cyano on your screen, you need more flow and/or more light.
If you smell any kind of "algae" smell while the scrubber is running, you need more flow.
If your tank has gotten rid of the nuisance algae, but cyano seems to be increasing, this is normal. Cyano does not eat nitrate and phosphate like algae does, so after your scrubber has starved the nuisance algae, the cyano has more room to grow. But if you keep your scrubber running strong and proper, the cyano will fade too.
If you have rubbery green algae, it means the flow is getting cut off and the algae is baking.
The best current spectrum for the bulb is 3000K (550 nm). This is yellowish-greenish, and it fits right in the middle of the red and the blue peaks of photosynthesis:
Pipe: Slots deliver much more water than drilled holes. Keep this in mind when figuring out how much flow you need.
Sump growth: Some people have open bulbs which light up the sump, and they are growing algae there. You don't want this to happen, so you need to use reflectors, or even foil, to block the light.
Coralline: Since phosphate will slow down coralline growth, you will start seeing more coralline as your phosphate drops in your water.
Advanced DIY trick: For those who can build such a thing, if you could build a top-off device which would shut off the flow to the screen, and then run your FW top-off water on it, then switch back to the regular flow, you would be able to extend the time between cleanings because the pods would be kept in control.
Dead fish: Scrubbers handle dead fish wonderfully; since ammonia is algae's favorite food, when a fish dies the algae will consume as much of the ammonia as it can, which could save your tank if the fish dies overnight. A skimmer, however, does not remove ammonia at all.
What equipment comes first: With regard to scrubbers, here are a few points to consider when planning which device should come before which other device (if you use them):
Skimmer: It should come before the scrubber and after the display, so that it does not remove the pods that come from the scrubber (if you need pods).
UV: Also should come before the scrubber and after the display, for same reason.
Mechanical filters/socks: Same as UV and skimmer. These trap food and pods (which rot and add Nitrate and Phosphate to the water), and thus should be the first thing you should stop using unless you change/clean them daily (but then you are removing the food for the corals.)
PO4/N03 removers: Really doesn't matter because N and P are the same throughout the system.
Fuge LR/LS/Macro: Doesn't matter, as far as nutrient removal is concerned.
Bio Balls (!): Should be removed slowly, unless you have massive amounts of fish, and little rock/sand.
Screens: I will be selling ready-to-use screens soon. But until then, it's best to use two layers of extremely-rough plastic canvas, using a hole-saw (and about an hour) to rough up all four sides of the two sheets: