Dual screens CFL ATS design

[hobbyist]

My 75G has been running for more than a year with an ATS as the only filtration (in addition to live rocks and a DSB). Everything has been working well with only fish and a few mushrooms. The only issue has been a few patches of brown diatom (or maybe cyno) on the sand bed.

Recently I added a few SPS frags and slowly lost them to STN. I thought lack of food was the problem and increased feeding to up to 32 ml of Brightwell Aquatics Reef Snow per day. This did not help with the STN but overpowered the ATS and the brown algae is now all over the sand bed and on some rocks as well. The algae on ATS turned from green to dark and slimy.

Strangely, throughout the whole time NO3 and PO4 have been undetectable using Salifert test kits. Then I found out about the Hanna Phosphorus ULR checker and got one. The PO4 tested out to be 0.07ppm instead.

Now that all frags are lost, I have stopped adding Reef Snow and am confident that the existing ATS will bring things back to the way it was.

While waiting for the existing ATS to work its magic I have decided to improve the design to better handle the feeding necessary to keep SPS.

The new design will have a few improvements over the existing one.

1. Can fit more bulbs while spreading them out over the screens more evenly.
2. More flow.
3. 3D growth.
4. Less bubbles.

Unfortunately due to space limitation T5HO is out of the question. So the design is based on CFLs.

Here is the new design.

[attachment=0:39v1i045]With cover.jpg[/attachment:39v1i045]

[attachment=1:39v1i045]Inside view.jpg[/attachment:39v1i045]

Two single sided screen with usable screen size of 13.5" x 9" each, which is about the same as one double sided screen with 120 square inches.

Lighting is by 5 23W stick CFLs, with a total wattage of 115W. The part on each bulb that actually emits light is about 1.5'' wide and 4" long. The bulbs are spread out as much as possible. The screens are about 3" from bulb surface, which should be far enough to avoid burning the algae.

Flow will be from a Herbie overflow with about 1,000 Gallon/hour. This can be throttle back a bit if it turned out to be too strong.

The side panels of the screen compartment are about 7" high to allow 3D growth and access to the screens without the need to take out the ATS box from the sump. Since the lower halve of the ATS will be in the sump, but above water, if the water level in the compartment goes over 7" it will just flow over the side panels into the sump.

The pipe fitting will be 1", if I end up with enough space to fit reducing bushings I may reduce the pipes to 3/4" after the tee. I read somewhere in the forum that higher pressure in the pipe is better, but I am not sure if this change makes any difference.

Another thing I am not sure is how to size the drains. To allow 3D growth I should have some water above the drain, would a 1" bulkhead allow that to happen or a 3/4" one should be used instead? Should the water drain out as gravity flow or full siphon?

[hobbyist]

[attachment=1:1xtncwgc]Screen.jpg[/attachment:1xtncwgc]

[attachment=0:1xtncwgc]Lights.jpg[/attachment:1xtncwgc]

[hobbyist]

[attachment=0:274vfldg]Screen with lights.jpg[/attachment:274vfldg]

[Floyd R Turbo]

A few comments:

Definitely 1" pipe. The pressure doesn't come from the pipe diameter, but the flow through the pipe.

Definitely 1" bulkheads and drains. You are not likely to get full siphon from the drains in the bottom of the box, but then again, I've never run one that way before. I do know that the one I was running maxed out the flow to the screen so the drain pipe was essentially a full siphon and 2 drains in the box were running with pretty good flow (all 1")

I would consider doing this as a single screen and trying to make it work that way. One double sided screen would be much more efficient than 2 single sided screens of the same size. You mentioned that you wanted access to the screens without having to remove the box. I wonder if this is why you are going down the 2-screen road. Well you're going to have to remove the box when you clean it each week, or at least every other week or so, trust me. You will get algae buildup in the bottom of the box. I ran mine for 3 weeks recently (from 100% clean after tear-down and move, and 1 week with no scrubber running) and the 3D growth at the bottom of the screen adhered to the acrylic and blocked the light to the bottom of the screen. I had always removed the box and cleaned it so this was the first time that had happened, but I've always had to clean algae off the acrylic. So splitting the screen up is not going to make your maintenance easier.

I would go single sided, enclose the lamps on either side and make some DIY reflectors, and maybe down the lamp wattage and go 3 on each side, and add a second drain in the box, or put one in the side up high and put a uniseal bulkhead in it with a small piece of pipe that would let the high-level water drain out against the sump glass. I don't know if that last part made sense, I can probably explain it better.

With a singe 13.5" screen, a 1000 GPH flow will probably max out the flow and your 2nd pipe will be running. You may consider teeing the drain line and putting a valve on the side that doesn't go to the scrubber. so you can tune it.

Just my 2c.

[SantaMonica]

The original scrubber, for whatever reason (have never seen it), was not keeping up. Thus the brown sand. So yes, adding liquid coral food is going to make it worse. You don't want to feed more until you've got strong green hair growth, and no nuisance algae in the display.

New scrubber: You definitely want 2-sided, so as to avoid dark sides which reduce filtering. I'd do two 23 watt bulbs on each side, with reflectors. Also dry-run it to check for melting.

I think a single 3/4 drain would be fine; I use that size for 800 gph. If you use two drains on the bottom, you won't get 3D. Overflow is not a problem in your case.

[hobbyist]

Thanks for the inputs.

I will change the design to one double sided screen instead and post the new drawings when ready.

[hobbyist]

Here is the revised design. A double sided screen with 2 x 23W CFL on each side.

[attachment=2:2lp6gb2j]Full view.jpg[/attachment:2lp6gb2j]

[attachment=1:2lp6gb2j]Inside view.jpg[/attachment:2lp6gb2j]

[attachment=0:2lp6gb2j]Separated view.jpg[/attachment:2lp6gb2j]

Both the screen and the box will be taken out for cleaning weekly. The two light compartment can be moved away a bit for easy removal of the screen box.

The usable screen size is reduced to about 95" (13.5" x 7"), due to single row bulb arrangement. 2 x 23W CFLs on each side gives total light wattage of 92W. Flow is about 500 gallon/hour.

Drain is 3/4". However, just for my own peace of mind, one side of the screen box is slightly lower, so in the case of overflowing water will just flow over that side down to the sump.

For reflectors, either mirror lining the sides and bottom of both light compartments, or individual bulb reflectors DIY from Aluminium beverage cans. Any idea which one would be better? Would the difference be significant?

If the lighting is increased to 3 x 18W or even 3 x 23W on each side, would it increase the performance significantly or at least proportionally?

I am also curious just how much better one double sided screen would out perform two single sided screens. 95 square inch vs 120 square inch, both with about 1W of light per inch, which means a double-sided screen would need to out perform by at least 26% to make the new design better.

[Floyd R Turbo]

Looks great! I would say you're going to get equal scrubbing power with that vs the 120 sq in double screen. The areas of the screen that get submerged under high-flow (3D growth) will have 2x the scrubbing power, so after cleaning it'll have a bit less power, later in the week it will have more. Also a single screen will get light to the 'roots' better, so algae will hold on to the screen better as there is better light penetration to the deep layers.

I like your idea of separate light boxes. You can move them away if they're too intense, so that's very nice. Any reflector would work better than none, but individual reflectors would probably work a little better. Going to 3x18W would give you a more even spread of light, but you might overpower the screen. Maybe not, I don't know. SM would probably know a little better on that one.

As for the emergency drain idea, that's a good one. I would put the lower side wall opposite of the drain side. You could make teeth like an overflow, or instead of a lower side, just drill a hole about 1/4 of the way down the side, which won't take away from the strength of the box.

also keep in mind that water on one side of the acrylic and heat on the other will cause the box to warp. You will want to reinforce the screen box on the outsides with crossbraces.

[SantaMonica]

I think making the light box out of all mirrored acrylic would be best. Although, the mirroring won't last forever in salt.

Your wattage will be limited by melting. Overpowering the screen is easily fixed by reduced hours.

A 2-sided screen is at least 100 percent stronger than a 1-sided one, with the same watts.

[hobbyist]

Thanks Floyd.

I do know that the one I was running maxed out the flow to the screen so the drain pipe was essentially a full siphon and 2 drains in the box were running with pretty good flow (all 1")

How much flow were you using?

I like your idea of separate light boxes. You can move them away if they're too intense, so that's very nice.

Good point. I did not think of it this way but good to know that the option is there.

As for the emergency drain idea, that's a good one. I would put the lower side wall opposite of the drain side.

What is the advantage?