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  1. #1
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    New sizing guidelines

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    What size scrubber do you need?
    (edited August 2017)


    Any scrubbing is good scrubbing. Even a small algae scrubber on a big tank will help your glass stay clearer, longer. But beyond that, the basic guidelines for algae scrubbers are based on how much you feed each day. These guidelines are to help you get the minimum size or number of scrubbers that will still do a good job of total filtration. You cannot "over scrub", so having a larger scrubber (or more of them) simply works more like the oceans and lakes do which have enormous amounts of algae to do all the filtering. And the scrubber can go anywhere in your system; it will filter the same.

    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 florescent watts (not equivalent watts) of light, or half that for LEDs, for 18 hours a day. If all 12 watts (6 watts LED) are on one side, it is a 1-sided screen. If the watts are divided on each side of the screen, it is a 2-sided screen. This 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)

    Problem rocks: Each 50 pounds (2.2 kg) of nuisance algae covered rocks you have adds 1 cube a day.

    Flow or air bubbles is always 24 hours; water flow 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 strings: Screen size is the size of the box (Length X Width), and is 2-sided because the strings grow in 3D.

    Clean algae:

    Every 7 to 10 days, or
    When it's black, or
    When it fills up, or
    When algae lets go, or
    When nutrients start to rise

    However these are just starting points; a lot of your tank filtering (especially in saltwater) is based on your rocks, so their condition plays a part too in what size scrubber to make, as well as what type of feeding you are doing, and what other filters you will be using. Here are some specific guidelines:

    FRESHWATER:

    Since freshwater grows extremely thin, long algae, scrubbers without strings are recommended. This is because you will probably need to clean the scrubber in your sink with a toothbrush (instead of in-place harvesting while still in your aquarium), and it's easier to brush a flat wall than it is to brush strings. So flat-wall scrubbers such as wide-panel bubble upflows work well in freshwater. Also, since the thin stringy freshwater algae will flow out of holes in the scrubber, if you put the scrubber in your display (where the animals are), they will learn to eat out of the scrubber and you will therefore be able to feed less. If you intend to do a large part of your feeding this way, multiple scrubbers will allow the feeding (and filtering) to continue in one when you have cleaned the other. Waterfall types are not recommended for freshwater because the long thin growth flows out of the drain.

    SALTWATER:

    With saltwater, you can get thick dense growth in the scrubber, which is when strings are an advantage (to hold on to the growth). So adding strings to a scrubber is acceptable and the decision is based on size and on where you want to put it, and also on how you want to clean it. Saltwater tanks which use live rock (even if the rock is "dead") will need to take into consideration the history of the rock: If it came from a tank with algae problems, each 50 pounds (23 kg) of this rock will add 1 cube a day to your feeding. This is because the rock is really just coral skeletons which absorbed nutrients from the water when the nutrients in the previous (or current) tank were high, and these nutrients will then start coming out and flowing into the water when your scrubber starts working.

    After looking at size, the main consideration is where you are going to put it. Since scrubbers filter the same in any location, it is just a matter of placement. Unlike freshwater, the thicker growth in saltwater usually does not flow out of the holes or drains as much, so you can't rely on it for automatic feeding (although you can manually take some growth out, and feed that). And similar to freshwater, multiple units are better than a single unit.

    REEF:

    Reefs are the same considerations as saltwater, with the exception that some people like the reef to run as natural as possible, meaning filtered by algae alone. With that in mind, here are some more details and options:

    1) If you are building a reef tank which is new, where the rocks are coming from the ocean or from a low-nutrient tank with no algae problems, and if you will just be feeding the fish sparingly, and if you DO want to have other filters and water changes, then you can just use the cube-feeding recommended sizes of the scrubbers.

    2) If you are building a reef tank which is new as in #1 above, but you DON'T want any other filters or water changes, then double the recommended scrubbing amount in #1. This will supply the corals and small fish with the most amounts of food particles, and will allow filtering and feeding to continue in one scrubber after you have cleaned the other.

    3) If you are building a reef tank which is new as in #1 or #2 above, but the rocks are coming a nutrient-problem tank which had measurable phosphate or hair algae problems, then the rocks will be soaked with phosphate and this will supply more phosphate to your new tank than your feeding will. So use the 50 pounds of rock = 1 cube of feeding guideline, to add to the recommend scrubbing amount.

    4) If you are adding a scrubber to an existing reef tank, and the tank has no measurable phosphate and no nuisance algae, and if you have other filters and water changes and you DO want to keep them, then you can just use the cube-feeding sizes of the scrubbers.

    5) If you are adding a scrubber to an existing reef tank as in #4 above but you DON'T want to continue using the other filters or water changes, then double the scrubber amount recommend in #4, preferably by having multiple scrubbers which are cleaned alternately. This will keep one scrubber filtering and feeding when you have cleaned the other.

    6) If you are adding a scrubber to an existing reef tank that has measurable phosphate and green hair nuisance algae on the rocks, and you DO want to continue using other filters and water changes, then you can just use the recommended cube-feeding sizes of the scrubbers. Use extra light (more LEDs) if possible because the higher phosphate in the water needs brighter LED's to make the scrubber grow green sooner. And if you double the amount of scrubbing (two units instead of one), the problems will clear up twice as fast because there will be twice the amount of algae absorbing the nutrients out of the water, especially when you clean one of them.

    7) If you are adding a scrubber to an existing reef tank that has measurable phosphate and green hair nuisance algae on the rocks as in #6 above, and you DON'T want to continue using other filters and water changes, then double the amount of scrubbing recommended in #6.

    8) If you are adding a scrubber to an existing reef tank that has NO measurable phosphate, but has LOTS of green hair nuisance algae on the rocks, then you need the strongest LEDs possible because the rocks are already full of phosphate, and the algae on the rocks is absorbing this phosphate, meaning you need the strongest scrubbing possible in order to out-compete the algae on the rocks. This is the hardest situation to fix, so you should use as much scrubbing as possible with the strongest LEDs available, and use as many other filters and water changes as possible too, until the algae on the rocks turns yellow and lets go.

    End

    NOTE: The following posts, below, were from 2011 (the old guidelines), and are not about the current guideline above.

    NOTE2: This calculator might help, if it is still working:
    https://docs.zoho.com/sheet/publishe...b2b670ae00412b
    Last edited by SantaMonica; 05-12-2019 at 02:27 PM.

  2. #2

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    Wow! This thread is an eye-opener! I just finished my first scrubber based on Floyd's Summary.

    http://algaescrubber.net/forums/show...cs-The-Summary

    Screen Size

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

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

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

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

    So, just so we're 100% clear on this:

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

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

    Horizontal: 4 square inches of screen material per gallon (4 square inches of illuminated screen material per gallon). Lighting must increase by a factor of 1.5 (discussed in the lighting section). Also note that this is a correction to what was listed on Post #1 of this thread (that post listed that a 10 x 10 screen was good for 40 gallons, instead of 25 gallons)
    I am running a 12" wide x 10" (1-2" in the water.) which is 96 sq in of exposed screen. Two sided so I am seriously over sized and under wattage. Correct?

    I have a 75 gallon reef with just 3 fish which I feed about 1/4 of a frozen cube per day. I had a horrible cyano and gha problem and it is all disappearing before my eyes with my new setup after only 7 days. I am going to do my first cleaning tomorrow after the full 7 days are up.

    So I could seriously use a 6"x4" screen?

    Time to cut a new slot pipe! lol

  3. #3
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    Yes way too big. You can use a tiny screen, limited only by it catching all the light.

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    Live Food and Sizing

    SM,

    how does feeding live foods such as decap. artemia cysts, baby artemia and rotifers compare to the frozen cube guideline?

  5. #5
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    You'll have to concentrate them and put them in an emtpy cube to see how many there are.

  6. #6
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    In other words, use a rotifer sieve to take out all the water. I would think you could feed a cubic buttload of rotifers to equal 1 cube/day.

  7. #7
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    Spot light CFL's work the best on small screens.
    150G. Reef/Mix
    125G. 3 Regular Oscars/1 Jack Dempsey
    75G. 20+ Africans
    40G. Fish/Reef. Algae Scrubbers on ALL my SW
    10G. SW Fish/Reef.
    10G. SW Hospital/new fish quarantine/pod breeder tank
    6 stage RO/DI system 200 GPD.

  8. #8
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    It's my preference, but I think a 2 cube/day screen is really a minimum, unless you know for sure that you're not going to feed any more than 1 cube/day. so 5x5, which is a nice fit for a 23W CFL floodlight on each side.

    the yellowing is because your screen is too large in relation to the feeding. 5x5 should green it up, but you may have to feed a little more, which your tank will like

  9. #9

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    Just curious, does a protein skimmer have any effect on the screen size?

  10. #10
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    Not really.

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