ALGAE SCRUBBER FAQ (12/17/09)

[SantaMonica]

ALGAE SCRUBBER FAQ (12/17/09)

Topics:

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




Scrubber News:

Product: Looks like semi-commercially made scrubbers will be available soon.

Reef Central: RC has removed its block of "scrubber" and "algaescrubber.net" and other terms relating to scrubbers.

Searches: AlgaeScrubber.net remains the #1 result when you search for "algae scrubber" on Google, Yahoo, MSN, and Ask.com


Scrubber Basics:

Q: Who owns AlgaeScrubber.Net?
A: His username is Worley.

Q: What are algae scrubbers?
A: Scrubbers are devices which use light and flowing water to remove the "bad" things (nutrients) from your aquarium water, while leaving the "good" things (food, i.e., 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 the algae scrubber, and then "clean" water comes out. Thus the water is "scrubbed" clean of nutrients.

Q: What are these scrubbers called?
A: They are called Scrubbers, Algae Turf Scrubbers (ATS), Algae Scrubbers, Algae Filters, Turf Scrubbers, 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 it properly (weekly), it may take a few weeks for the screen to be 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 rough screen, and weekly cleaning 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 that one side. You don't need to include the volume of the sump, unless it also has livestock in it that you feed.

Q: Will a scrubber harm my corals?
A: No. As a matter of fact, corals grow best with lots of food particles in the water, and corals also like low levels of nitrate and phosphate. 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: 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 then 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 cup though.

Q: I'm currently building my tank. Should I wait to install my scrubber?
A: No. Scrubbers eat nitrate, phosphate and ammonia, and that's just what cycling produces. By starting a scrubber early (even during cycling), the screen will be ready for adding livestock sooner. The screen won't grow a lot, however, until you start adding the livestock.

Q: I'm still designing my system. What other filtering devices besides a scrubber should I buy?
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 (or improve your current) scrubber, 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 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, then yes.

Q: Where can I buy a scrubber?
A: Nobody currently manufactures or sells scrubbers. After 1.5 years of waiting, however, one will be available shortly.

Q: Can someone build one for me?
A: There is a list of builders here:
viewtopic.php?f=9&t=25

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. It makes the difference between a tank that has "not much algae", and one that is "spotless".

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 using a hole-saw in your hand. It should feel like a cactus, and be rough enough to almost cut your hand. The rougher it is, the faster algae will grow on it, and the longer the algae will hold on.

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 it, the more algae will remain, and thus the faster filtering will continue. If you have two separate screens, you can clean one completely since the other one stays filtering.

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 eliminate nuisance algae (and glass cleaning) then you'll need a scrubber in addition to a skimmer, because a scrubber removes 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 July 2008. But it is now known how to easily build and use a scrubber to do all your filtering for you (just like in the ocean). It is cheap, easy, and best of all there is NO possible way for something to "go wrong" with a scrubber and have it 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) way to start out.

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 were reefing in the 1980's and 1990's when scrubbers were built and operated incorrectly. Scrubbers back then 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: A vertical screen 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 self-limits unless you have a LOT of flow. With a vertical, however, the flow is rapid and goes right over new growth. (This is in addition to the fact that a horizontal still needs twice the screen area, since it is one-sided.)


Scrubber Lighting:

Q: What kind of light do I need?
A: Experience has shown that at least a 23 Watt Compact Fluorescent (CFL) floodlight, of the 2700K or 3000K color, works best. One on each side of the screen, about 4" from the screen, and pointed at 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 has also shown tremendous growth, although they are more difficult to design and build, however their even spread of light from side to side is superior to CFL bulbs. And recently, it has been found that there is an upper limit on CFL bulb size; CFL bulbs in the 50 watt range are at the top, whereas anything in the 60 watt range is too much. If you must use 60 watts or more, then use two smaller bulbs instead. The lighting just needs to be spread out more, and not concentrated so much on one spot. And whatever wattage you use, always get a "floodlight", which has the reflector built-in. If you already have bulbs and they are not floodlights, be sure to get "CFL reflectors" so you can point the light at the center of the screen, and not waste any.

Q: What if I can't put a light on both sides?
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: 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 twice the size. 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 to 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 50 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 55 watt bulb, but you can have multiple smaller bulbs, of course, in order to reach your recommended total wattage. The ultimate are TH5O bulbs, which spread the light out so that the most light-power can be placed near the algae, without "burning" it.

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.

Q: How long should I leave the lights on?
A: 18 hours. 20 hours max. Never run the lights 24/7, because the algae will "burn" and stop growing near the light. Algae needs rest. Amazingly, algae continues to do some filtering even in the dark.

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 CFL for every gallon (3.8 liters) in your system. 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: 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 35 gph, and a screen two inches wide would need 70 gph, etc. More is even better. Less means less performance. And if you are making a one-sided screen, you then want all that flow on the one (top) side. This is because fast flow is critical, and horizontal screens do not have fast flow. You make up for this by putting all the flow from a two-sided screen onto the top side of a one-sided screen. All flow will be limited by the roughness of your 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 also the less nitrate, phosphate, and nuisance algae you will have in your display.

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.


Scrubber Results:

Q: What can I do to get the best results from my scrubber?
A: When building, use the highest power bulbs that you can (up to 45W bulbs), and put them within 4 inches (10 cm) of the middle 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 getting an "oil slick" on your screen.
A: "Oil slicks", or very dark or black algae, usually happen 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), 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 does the same filtering. They are just different types of algae depending on how high your nutrients are in your water, and how strong your light is. Continue 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 with other filters/waterchanges 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. Aluminum tape, or a piece of long plastics, 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 less wide (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 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, 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 macros?
A: This is a long one, and is detailed here:
viewtopic.php?f=9&t=67

Q: How does a scrubber compare to a coiled denitrator?
A: A denitrator removes nitrate. A scrubber removes nitrate, nitrite, ammonia, phosphate, CO2 and metals. 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 they may lower the pH while doing it. And they are expensive to refill. Scrubbers remove phosphate, as well as nitrate, nitrite, ammonia, CO2 and metals, and do so while increasing the pH. And once built and installed, a scrubber does 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, 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. Scrubbers don't "store" phosphate; the phosphate is "in" the algae that grows, and it is then removed during weekly cleaning.

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). 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.

Q: How does a scrubber compare to bio balls (wet/drys)?
A: Bio balls (trickle, not submerged) aerate the water, convert ammonia to nitrate, and trap 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 food that are alive in the water. A scrubber reduces nitrate, ammonia, 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 (for when you add new fish).


Scrubber Applications:

Q: Can I put a scrubber on my nano?
A: Yes, you can make/put a scrubber on any tank. There are two types of nano's: Those with a hatch on the top that let you get to the filter area, and those where there is no hatch (like Aquapods) where the whole lid opens up as one unit. Aquapod types are the hardest to add your own scrubber to; however the hatch-on-top types are the easiest.

Q: Have scrubbers been used for breeder or retail tanks?
A: They are being tested now.


Scrubber Advanced Topics:

Q: What exactly does a scrubber do to my water?
A: It takes ammonia/ammonium, nitrite, nitrate, phosphate, metals (like copper and iron), and CO2 out of the water. It puts oxygen into the water. It also cools the water if you have an open unit. And if you put a fan on it, it REALLY cools the water. Increased evaporation, of course, will also occur, unless you use an enclosed unit. Copepods are added to the water. Iron and Iodine are removed from the water, but they are of lesser importance, and are removed to a lesser degree, than the above items. 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.

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 as removing nitrates and phosphates is like saying that removing BEER before you drink it is the same as removing pee after you drink it. Wouldn't you rather have the beer, and remove the pee? Skimmer remove the food that you put in the tank, period. If removing food is what you need, then a skimmer is a must-have.

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. But twelve hours or longer, and you will probably loose your scrubber (but your tank will be gone too).

Q: I've heard you have to "pulse" or "surge" the water to get best results.
A: This is not proven yet. Most scrubbers use a constant flow, and have great results. Thus it is not recommended to use a surge device. Plus they 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.

Q: How long does it take to get the real "red/brown" turf?
A: You won't, unless you pulse the flow with a surge. All algae is good, however, no matter what color or texture it is. Real red/brown turf just filters the most for a small size, that's all. But it's not like other algae take up a lot of space.

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.)

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.

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 the bacteria themselves are food for corals. But also you need to know that recent research has shown that skimmers themselves 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.

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.

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.

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.

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 a few 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... all over 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 the lower part of a screen is not as effective as the upper part, since the water flowing over the lower part has already been filtered by the upper part. So a screen that is not tall (no lower part) makes up for it by being wider. In effect, the whole screen becomes the "upper part". Wider screens also make use of 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 bought a pre-grown real-turf screen; how do I take care of it?
A: First, real turf needs a surge to stay alive. If you are just flowing water constantly, real turf will eventually give way to regular algae. Second, Real red/brown turf is a little different from other algae. Since it's so thick, it packs all the nutrients into a very tight space. Thus is does not need to be cleaned off the screen as often. Also, when it is cleaned, a razor blade is usually necessary to scrape it off. Scraping a real turf screen is usually done about one time per month. However, green hair algae and slime will cover the turf quickly, and pods will eat it quickly, so you still need to "clean" the turf in your sink with freshwater every 7 days. 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 fourth week, do a full scraping with a razor. All in all, real turf screens are probably not worth the trouble.

Q: I travel quite a bit, and sometimes 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 (3.8L) 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 FW 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: No. 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. 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.

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.

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 gets 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.

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. This way, the other screen only has to wait 10 days before it's trip to the sink (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: Not really. 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.


Miscellaneous:

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 still did not sell scrubbers to the public; he also did not allow others to sell them. 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". 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...
http://en.wikipedia.org/wiki/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, water changes.

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

Ammonia Removers: Bio balls, live sand, live rock, poly filters, Prime/AmQuel, 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 cleaning; 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 July 2008), or the scrubber in question was built incorrectly or is being run incorrectly, which does happen in DIY designs.

Q: I've heard that these "waterfall" type of scrubbers are not real "ATS" 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 trademark "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 one at that time. But this person also made ATS designs that did not have dumping mechanisms at all.

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 .03 is going to slow down or stop coralline. Since a scrubber will reduce the phosphate to less than .03, it will allow the coralline to flourish, if not take over.

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 and 1990'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 the 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.

Q: I'm keeping my skimmer. When I add a scrubber, should I expect the skimmer to produce less foam?
A: Not really. 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).

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.


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