Who's tried skimming like this?

[ChrisRD]

I (hopefully) will be setting up another tank soon and thought about using a recirculating needlewheel skimmer (I have a Euro-Reef laying around I can easily convert). I'd like to feed the skimmer via the overflow drain from the display tank.

What I'm considering is using a smaller return pump and putting ALL of the drain flow through the skimmer. Considering the recommended feed rate for a recirculating skimmer this size, I should still be able to manage between 2X to 3X sump-to-display turnover.

Anybody try this? Seems like it would make for some real efficient skimming...

 

[Len]

Deltec recommends you feed their recirc skimmers directly from the overflow. However, the recommended flow-through rates are REALLY low: about 1-2gph per total tank volume. I don't know how true their recommendation is, but they discourage ramming lots of water through their skimmer. If you follow their recommendation, it's practically impossible to run the entire overflow drain through your skimmer

From experience, problems running lots of water through a recirc needle wheel include:
1) Too much water and foam in the skimmer body. Recirc needlewheels will generate a very high proportion of foam/air which will displace a lot of water in the skimmer body. If you channel lots of water through the body of the skimmer (even with the output fully open), the water line will be that much higher. Your neck had better be very tall to accomdate high flow plus all this air. Chances are, your cup will skim extremely wet
2) Too much turbulence. I'd imagine a lot of high velocity flow can't be good for foam formation or contact time.
3) You'll get bubbles galore coming out of your output. I know when I have too much water going through my Deltec when I see a lot of bubbles escaping the output.

Personally, I'd tee the overflow off so you can control the amount of flow going into your skimmer.

 

[Anonymous]

As Len said, T-ing off the overflow would probably the way to go.

Personally, I think Calfo's suggestions to try to harvest as much surface from the display as possible is probably overstated. The typical reef tank has so much turnover, I doubt the surface film is present long enough to be substantially different from any other bit of water in the system.

 

[GSchiemer]

I agree with Dan and Len. I think the efficiency of the skimmer will be impacted by a large flow-through. I also think it will be hard to maintain an adjustment level. Personally, I've always felt that the best way to feed a skimmer is with a dedicated pump.

Greg

 

[Anonymous]

I built a home made that used the overflow to feed the skimmer and then had a "deep water" air pump to make bubbles via limewood airstone. Some issues I came across was keeping the water level constant in the skimmer, now I had a double U design so the water level should have been constant but the issue is the speed the water went through which did tend to vary, now I'm unsure if that's due to the fact siphon overflows just suck that way or what, either way I disassembled the skimmer after a while (and massive cyano outbreak I'm guessing from missed nutrients).

 

[ChrisRD]

I definitely agree that forcing too much water through the skimmer would be detrimental. What I'm asking is if you're well within the recommended feed rate for the skimmer.

Taking Len's Deltec example, I'm assuming the "H20 Throughput" shown is their specs is the recommended feed rate, correct? I'm talking about putting something like a Deltec AP600 (rated for 160 GPH throughput) on a 75 gallon tank with a return pump that's giving you about 150 GPH (2X turnover) after losses. Seems like it could work, no?

Dan makes a good point about the surface film. I was actually thinking more along the lines of improved detritus removal with this setup.

[edited to correct typos!]

 

[Len]

Ah. I didn't know you were aiming for that low a gph through the sump. It could work. However, if you're using a Ca reactor in the sump or your heater is down there, such a slow return gph may create other issues.

 

[ChrisRD]

Yeah, that's one question. The other is whether or not this setup would actually improve detritus removal. If not, probably not worth doing IMO.

It seems to me if all flow is going through the skimmer it should result in more detritus getting skimmed out. OTOH, with the lower turnover rate, maybe less detritus would make it into the overflow and out of the display tank which would be counter productive...

 

[Anonymous]

Even with that low of a turnover through the sump I would still agree with the recommendation of a 'T' with a gate valve on the bypass side and a pump slightly bigger than what you actually need for the skimmer. It's easier to precisely control flow through the skimmer using a gate valve than a specific sized pump. It would just be for fine tuning and nearly all of the flow can still go through the skimmer.

JMHO

 

[GSchiemer]

I don't believe it would improve detritus removal because most detritus isn't carried on the skimmer foam but tends to sink to the bottom.

Greg

 

[ChrisRD]

I was thinking it might increase the percentage that gets taken out by the skimmer. If so it would provide a means of actively removing some of it from the water column rather than just trapping/accumulating it somewhere for periodic removal.

Based on the responses maybe I'll just stick to a more traditional setup and the ol' syphon hose... :wink:

Thanks for the replies.

 

[ereefic1]

I'm running a large MRC recirculating skimmer and recently hooked up 2 of 3 drains to feed the skimmer. It appears to me that it is pulling out more than when it was being fed from the 100gal. stock tank sump.

 

[Ben1]

Seems to me like it would help. If the turn over in tank is high enough for the detritus to stay suspended it will go over the overflow. You return pump being smaller is a good idea as it allows more time for the skimmer to process the water and less will actually bypass skimming at all.

If you set up your skimmer using Calfos methods and then just in an open sump it is obvious that allowing it to pull more from the raw overflow water brings better skimming.

If you try it and compair the amount of daily skimmate to when the skimmer just sits in an open sump you will most likely see a signifigant increase of skimmate. I saw a major increase in my daily skimmate by just making this simple change to how I set up my Euroreef.

I also feel that a tee would work out well or just letting your feed pump pull from a small partitioned area in the sump that the raw overflow water is directly feeding into also.

JME

 

[ChrisRD]

Thanks for the responses. I think I'll set the tank up so I can easily switch configurations and see how this compares to a more traditional setup.