Looking for a bit of help on a design.

[wmilas]

I'm in the process of setting up a large system. I have a 660 gallon display, 175 gallon sump, 65 gallon fuge, 40 gallon frag and 40 gal quarantine. The system has been up for about 2 months now and is at the end of its cycle. I started with a good chunk of live rock, no bio load, and thus the cycle was extremely fast. I'm pretty much just leaving the system fallow except for snails, chaeto, and dosing phyto to encourage pod growth.

My last system was years and years ago back when skimmers were relatively new. I used a dump style ATS that I built for my last tank. This was when we were first starting to be able to keep hard corals successfully. Anyways I have a confession to make. I went out and bought an extremely large (and expensive :( ) skimmer for my current system. I guess I didn't do enough reading (although I've been planning this system for years) and just assumed the biggest and most efficient skimmer is what I wanted. Well, I got exactly what I wanted. I have an ATB XL and the thing is a beast.. works great. Too good. It will pull ALL of the phyto and pods out of my water. Withing 3 days of it running pods are undetectable, and phyto is completely gone from my tank. The only pods that survive are the lucky ones that live in my fuge and hang on for dear life :)

This is not exactly how I wanted to run my system. I don't know what I was thinking but I'll admit I messed up. So I'm looking to build an ATS. I've read all the info I can but I would like some feedback on what I'm planning.

To start with, my build thread is over at RC at: http://reefcentral.com/forums/showthrea ... id=1354165 (http://reefcentral.com/forums/showthread.php?s=&threadid=1354165)

You can scroll through it to loom for sump pictures but here is probably the latest ones:
http://openprojects.rarcoa.com/~thebard/_MG_4936.jpg

Here is a much older picture of the sump to get some idea of the dimension:
http://openprojects.rarcoa.com/~thebard/_MG_4314.jpg

Sump is 48x24x36. As you can see the sump has a large bubble tower and skimmer. Both are sitting on a platform. The skimmer can be removed and the bubble tower can be pushed into a corner and made smaller if need be. So how to design an ATS. The pump feeding the tank is a Dart. Its currently dialed down to around 50% flow. The plan is to feed off the dart to power the ATS. I'm thinking of 2 panels 20" wide. That should be 1400 gph of flow which I easily have excess from the dart. I'm thinking each panel 30 or 36" high. 36" would give me 1440 sq inches.

How to light it? thinking of either using CFL's with reflectors for the "ends" and bare cfls in the "middle". Or t5's although I'd have to go probably 2 horizontal lights per side, so 8 lights total. Not sure How to attach them. I can either hang the panels from the ceiling, or stands in the sump. If I make stands I can make little arms that hold the t5's horizontally. I don't know. Any ideas?

[SantaMonica]

Couple of ideas. First I need to know a few things. Is excess light going to be a problem? Is the sump 24 or 36 wide?

A dual-screen is always a good idea. But to make full use of the redundancy and "always-filtering" ability, one screen needs to be running while the other is being cleaned. This means separate pumps for each one. Can you do this? One way is to feed one with the dart, and the other with a separate pump (cheap is ok). Another is to not use the dart at all, and use two cheap pumps. It's nice to be able to work on the scrubber for a while, but still have circulation to the tank.

Concerning the use of your bubble towers, you might instead consider feeding one screen with the overflow. This would "probably" stop the bubbles, as well as eliminate a pump. (the bubbles have a long path down the screen, during which they are only 1/4" or so from escaping into the air). Screens do a good job of bubble reduction.

For lighting, let's assume your screens are parallel. The outside lights are easy; one of these on each side (2700K version)...

http://homeharvest.com/hydrofarmcompactfluorescents.htm

For the center light, it depends on how much space you have between the screens, and how much extraneous light you can handle. The easy way is to just hang one or two CFL bulbs (same bulb as above light) in between the screens. If you need to block the light, you could build a light-shield around the edges. I think this CFL method is much easier than trying to mount multiple T5's in there. But if you wanted to spend the time, the T5's would be very near to the screens, and would be consistent from edge to edge. Watt-for-watt, T5's would be better.

One consideration on a large scrubber like this is to have very easy screen removal. Although It's bigger, you still need to be able to whip those screens in and out with no hassle, connections, binding, etc. And you need a flat surface that you can lay the screens down on, so you can press down hard with a scraper, to clean.

[wmilas]

Excess light is not a problem. All the equipment is in a sealed fishroom. I can do whatever I like in there :)

The sump is 24" wide, 48" long, 36" deep. I have no problem with the top of the screen sticking out of the sump vertically. Ideally I'd like to run the sump half full of water... and thats approximately where its running at now.

I'd rather avoid separate pumps. I'll put a gate valve on the T for the scrubber. I'll then but 2 ball valves, one for each screen. This way I can adjust flow to exactly what I want for the scrubber, and then be able to turn off one, or two screens. This will make servicing each screen easier. I can still have circulation to the tank this way also.

Concerning the bubble towers. I had written a long paragraph on why this wouldn't work. I just erased it. The more I think about it, the more I like the idea. For a moment disregard the the sentence above, and about T'ing the dart for the scrubber. If I take the 3" return and T it off into into 3x 1.5" screens and run them width wise parallel off the sump it might work. Each screen would be approximately 22" long and I'd make them 18" or so high. I would support them right on the lip of the sump. I would hang two of the large bare bulbs between the 3 screens, giving me the center screen double and the ends single. If I needed more coverage I would put a 4th screen on and hang another bulb between the 3rd and 4th screens giving me 2 doubles and 2 singles. Does this make sense? Its not as efficient as having bulbs all the way around but it does maximize the watts at the expense of space.

How far apart should the screens be? Assume the bulb is what, 2" in diameter? 10" would then give me 4" to each screen.

How would I secure the screens to the tubes? Do I want to permanently affix the screens to the tubes and pull the tubes off via a union (sounds like a pita) or should I somehow affix the screens to the tubes so I can remove just the screens and clean them?

How important is that flat area to scrape? I have a utility tub. I need to measure the tub and see what size screen I can fit flat. Each arm might have two screen segments, 11x18".

Any of this make sense?

[SantaMonica]

How far apart should the screens be? Assume the bulb is what, 2" in diameter? 10" would then give me 4" to each screen.

If you do 22" wide screens, and if you used the drop-in CFL 125W bulbs, you'd need 2 bulbs between each screen. 4" to each screen is good, but you could go 6" if needed, because they are powerfull CFLs. One bulb in the middle, however, is just too far for the light to be effective at the edges. T5's of course would remedy this, at the expense of complexity (you'd need a T5 every 4 inches or so.)


How would I secure the screens to the tubes? Do I want to permanently affix the screens to the tubes and pull the tubes off via a union (sounds like a pita) or should I somehow affix the screens to the tubes so I can remove just the screens and clean them?

Just use tie-wraps like everyone else. They work great. You need to be able to remove the pipe (with a union) and the screen (by cutting the tie wraps), so that you can clean up into the slot. Look through here for examples:

viewtopic.php?f=3&t=26 (http://www.algaescrubber.net/forums/viewtopic.php?f=3&t=26)


How important is that flat area to scrape? I have a utility tub. I need to measure the tub and see what size screen I can fit flat. Each arm might have two screen segments, 11x18".

It won't be needed for the first few months. But later (if you are running it right) you'll no longer be able to just spray or push the algae off. By the way, you might consider using two layers of screen, tied or melted together, to give the algae even more places to grab onto. This is not critical with a multi-screen setup, but it does help keep the filtering from going to "none" on a screen after cleaning.

[kcress]

wmilas; First let me say you have a nice setup! Also nice to see someone with an open mind.

I think you should consider using four screens. Split each of your proposed screens in two. Smaller screens are much nicer to work with and will fit your sink with no issues. Also 4 screens will let you change how you clean them - both sides of one, or half of two , etc. It would allow you to remove 1/4 of your cleaning power if you want to. Also you could start with one and add more as your tank loading goes up.

I'd run a valve for each. This would let you turn off a screen.

Just my thoughts.

[wmilas]

Ok good info all around. I measured my utility tub and its shortest dimension is 23" so I'm ok. I can always have the long side of the screen stick out a bit, as long as I can get a good portion flat on the bottom.

I might consider hanging 2 bulbs per center. It would let me fool around with wattages and K values. I'd like to stay away from the super high wattage bulbs as they require mogul bases. I could hang a pair of 60 or 85 watt CFL's per center though.

kcress: when you say 4 screens, do you mean 4 22"x18" screens, each with its own water flow (ie 4 slots) or do you mean 2 slots with screens doubled up, or do you mean 2 slots with each screen 11"x18" sitting next to each other to make one big screen?

Also as far as having an open mind, I'm not running the skimmer right now anyways and I'll always have it. All this is going to cost me is a little for the materials and a weekend to make. If it doesn't work, I can always just go back to the skimmer. No big loss :)

Te valves bring up an interesting problem. Let me start at the beginning. Right now I have 2 over flow boxes each drilled for 3 bulkheads. One in each overflow are dursos. One each are emergencies with just an open standpipe, one each are capped. The dursos and emergencies all feed into *1* 3 inch tube. Because I have to travel such a long way from the tank to the sump I elected to go with one oversized drain.

The problem arises that if I feed the scrubbers from the overflow, and I balance the flow with the dart (ie I slow the return into the tank just right so I get sheeting action) and one of the slots clogs up, I'm going to have a tank overflow. The problem is I don't know how to get "around this". My first thought was to take the 3" pipe reduce it down to 2". Then use 2" along the back of the sump with 2" T's. The slot pipes would be 1.5" or 1" depending on the amount of screens. I'd use 1" pipes for 80 linear slot inches, or 1.5" pipes for 40 linear slot inches. My dart going full bore can power 80 linear slot inches at 35 gph per slot inch. Ok so with this in mind there is no where for excess water to come out, just the slots. Since the slots aren't being fed from the dart directly, just from the overflow, the water isn't pressurized. If one slot clogs for some reason, I don't think the other slots will be able to handle the flow because they aren't pressurized.

How to resolve this issue? I could make a relief dump valve of some sort at the end of the overflow. The problem is how to control the water going to the slots then? If I just let the 2" pipe at the end exit into the tank I don't see the slots getting an even amount of water. IF I put a valve to control the exit, I have the same problem with the overflow. I could In theory have the 2" pipe go up, to just under the high in my tank then do a 180. If slots backed up and water pressure built, water would climb until it went over the 180 thus causing a siphon and draining and it would repeat making a bunch of noise. I guess that would work?

[SantaMonica]

The problem arises that if I feed the scrubbers from the overflow, and I balance the flow with the dart (ie I slow the return into the tank just right so I get sheeting action)

Actually you don't want to slow the flow for the sake of the screen. You want full flow all the time, and then you size the slots in the pipes to handle the flow. The more flow, the better. You can't have too much.


and one of the slots clogs up, I'm going to have a tank overflow.

No, for four reasons. First, screens never "clog up", the way you are thinking. There is nothing that can get into a pipe and all-at-once block a 22" slot. What really happens is that if you let the growth go too much, some parts of the screen grow up into the slot and slow down the flow there. This causes the rest of the slot to flow more. And this higher flow pushes out algae if it tries to grow here. So you end up with vertical strips of high-flow, high-growth, and other strips of low-flow, low growth.

Second, you can, if you want, install a "light shield" along both sides of the pipe to block light from reaching the slot. This prevents any light, and growth, from reaching the slot at all.

Third, with 4 (or even 2) separate screens/pipes, if one did start to slow down, the flow would increase to the others, thus balancing out.

Fourth, you could use a "bypass", which negates the entire clogging concern. It's the "optional drain" in this pic:

http://www.radio-media.com/fish/OverflowFeed.jpg


But of the many many overflow-fed scrubbers built so far, I've not heard a single report of one ever "clogging" the way you are thinking.

[wmilas]

Thant makes me feel much better.

So realistically speaking, if I have 18 inches of screen vertically, and each slot is 20" my maximum (4 slot) system would be 1440 sq inches. Is this overkill? I planning on having a natural mixed sps/lps tank with a medium to high fish bioload. I don't want to build something really really huge if I'm only going to use, say, half of it.

[SantaMonica]

It's not really 1440, because the outside screens are one-sided. The one inch per gallon is for two sides screens, of average load. Plus, yours will be high load.

[kcress]

wmilas; I was suggesting the same original screen area just breaking it up into smaller pieces.

If you are still concerned about a clog you can use a stand pipe just before the point where your overflow reaches the screens. Here's how you'd do it:

Place a tee, say a 3 x 2"threaded x 3 with the 2 vertical. Screw a valve into the 2" temporarily. Set up your screens and get them going the way you want them. Screw a friction fit pipe into the valve that is a foot or two high. Open the valve. The water will seek a level no where near the height of your tank because of the flow out of the screens. I would guess perhaps 8 inches. Measure this and cut the pipe to this height plus whatever you deem reasonable,(maybe another inch or 2). Replace the valve. with a glued up threaded piece of pipe. Now if your screens get blocked the back pressure will rise to the point that this standpipe overflows into your sump. You can add angles to get this back down to the sump to limit splashing if you want.