Troubleshoot my design

[Nathan]

Hi all!

I am a newbie to algae filtration, so I hope you will pardon my ignorance. I'm interested in setting up an algae scrubber as a phosphate remover for a 300 gallon freshwater display tank at a school. The tank is a bit odd; I inherited responsibility for it and have no idea how it was initially set up, but now it looks like this:



There is a false back that houses the filtration area. The false back is divided in two; water from each side goes through an overflow near the center of the tank, under and then over partitions, then spills into a large chamber with two pumps at the end. There are several partitions, open at top and bottom, in this larger chamber which I believe are meant to separate media types. I would like to install trickle plates across the tops of these partitions in order to create more of a wet/dry situation and use more of the available media volume. It occurred to me that it might be possible to make the trickle plates serve double duty as an area for algal colonization. I have two fluorescent fixtures that I can set up above the trickle plates, each of which takes two 14 watt T5 lamps. Each trickle plate would be about 4" X 30" and receive ca. 800 gph flow. I have additional pumps which may be brought to bear if necessary. My initial plan for building the trickle plates is to use acrylic sheets with holes drilled in, with three layers of needlepoint canvas placed on top.

So a summary:
300 gallon tank
total 1200 in.² scrubber space, mounted horizontally
56 watts of fluorecent light, top side only
ca. 1600 gallons per hour over scrubbers, can be raised to 2400 gph

What do you think? Will it work? I realize this scrubber will be inadequate as sole filtration, but it won't have to be; the bacterial filtration will remain intact (and will hopefully be much improved by the addition of the trickle plates).

Any help is much appreciated!

[Nathan]

Sorry, that's 240 in.² of scrubber space. Must have had a neuron misfire.

[SantaMonica]

If you have no rock/sand/wood, then you'd probably want a bio-ball setup. A scrubber won't work for bacterial growth.

General rule for scrubber size: 1 sq in per gallon if two sided; 2 sq in per gallon if one sided (yours is 240 one-sided?).

General rule for lighting: 0.5 watts per gallon for medium filtering; 1.0 watts per gallon for high filtering.

[Nathan]

Thanks SantaMonica! I should clarify: the filtration area does contain media (both mat media and bioballs), it is just that the current setup only lets water flow through the submersed portion of the media; I wish to turn it into a wet/dry style setup with supplemental algae scrubber. Yes, my potential scrubber area is 240 in.² one-sided, as I can only light the top portion.

I forgot to include this diagram of my proposed setup:

[SantaMonica]

Well the situation is that if you use strong lights (300 watts total), AND if you don't mind cleaning one screen every three days or so, then it will work. [I use 100 watts in my 100 gallon.]

Since the screen is so small, you have to make for this by using a high power light. But a high power scrubber grows very quickly (which is how it makes up for being so small), and thus it must be cleaned more often... or else the bottom layers start dying.

So if you can use 300 watts, and you can clean one screen every three days, you can probably get away with average stocking, but not heavy. If you did try to stock heavy, your nutrients would never get to low levels, although they'd certainly be lower than without a scrubber.

[kcress]

Any chance for a picture or 3?

[Nathan]

Thanks again, Santa Monica. I'll have to think on this a bit; I would rather avoid high-wattage lights if possible. I'll try to figure out how to add an off-tank scrubber without drilling the tank.

KCress- sorry, I can't get a good shot of the filtration area simply because there isn't enough space behind the tank. I don't have any recent shots of the display itself, but I'll take one tomorrow and put it up if you like. It's stocked with local native freshwater fish- redspotted and dollar sunfish, central mudminnow, and several cyprinid species. All the fish are currently small but most have a good bit of growing to do; some of the cyprinids will reach 10-12". The substrate is a deep bed of soil and leaves topped with gravel, plus driftwood, limestone slabs, fossil corals, coontail (Ceratophyllum demersum), and eelgrass (Vallisneria americana).

[kcress]

Don't worry about it Nathan.

I was just having trouble with understanding where you were putting the screens.

I could not imagine having them in a back sump area and having them work. I also can not see how having them on the top would not block the lighting of the tank itself.

Also if you are actually trying to teach students about the entire biological process, the ecosystem, the tank represents, having any filters hidden in the back seems to be a lousy tool. If you are only interested in the fish themselves anything would probably suffice then.

If you remote the turf scrubber, is there any way to use direct solar? Perhaps put the screen system on a sunny window sill?

[Nathan]

The scrubbers would only be above the false back, not above the display area, so no light would be blocked. Maybe this is a little more clear:


Having the filtration on display would be, in my opinion, fantastic, but the higher ups at the school wouldn't go for it. I think they would be much happier if the tank were set up with blue gravel, plastic plants, and castles. The tank is in the building's lobby, well removed from any windows; there is a skylight, but in order to take advantage of that, the scrubber would need to be out in the middle of the floor, which again would upset the administrators.

[SantaMonica]

Well if teaching is the main focus, then you could do it as drawn, and explain how the scrubber is doing what it does. Any nutrient drop would then be a bonus.