Recirculating skimmers a gimmick????

[prance1520]

LOL, exactly. The idea of recirc isn't a gimmick, but the price hike? Ehhhh....

 

[UCanDoIt]

<a href=showthread.php?s=&postid=8928570#post8928570 target=_blank>Originally posted</a> by Fishbulb2
..... Most recirc skimmer recommend only about 1-1.5X flowrate through their skimmers which leaves the water in the reaction chamber for a lot longer. Most non recirc skimmers have a much faster flow rate through them and thus probably not enough time for some organics to fuse to the bubbles.
FB

The recommended flow through rate for the high end skimmers like H&S is 1x-1.5x, but no more than 2x or no more than the rating of the skimmer's capacity. Higher flowthrough rates on a H&S skimmer could make it too turbulent inside the reaction chamber and the foaming will have a difficult time forming. I have my H&S A150 on a 175g FOWLR tank and the flowthrough rate is approximately 225-250gph.

 

[manderx]

High quality skimmers properly sized to the existing bio-load are not in the need of having their reaction chamber water re-circulated!

that's missing the point of a recirc skimmer. it's not to recirc the water in there longer (though you can trim down the feed and get that effect if you wanted it), but to inject air without having to inject new water at the same time. this lets the pump do more work injecting air since it does not have to lift the entire column of water along with that air.

though one drawback to recirc is i think proteins get stuck to the bubbles faster and easier while exposed to the huge sheer pressures within the needlewheel (or beckett or whatever) so i want my dirtiest (raw feed) water to go through there before it gets diluted by the cleaner water already in the body. so to me with current recirc designs i think it's a trade-off for more bubbles vs dirtiest water going through the gauntlet and perhaps loading up better. depending on the tank/pump/flowrates, one might be better than the other. i think i am going to make my next DIY skimmer a recirc with the feed down in the pump inlet plumbing.

these people reported better results in the recirc mod

it's easy to see what you want to see, especially with something as subjective as skimmate production when you are proud of yourself for doing a DIY (or spending the premium on a store-bought). heck, it could be something as simple as while doing the mod they went ahead and gave it a good cleaning at the same time, and being cleaner made it skim better, and they were being extra attentive watching for results from the mod.

Some DOCs take minutes to fuse to a bubble

randy doesn't agree with this. he says it's a simple matter of concentrations, so you want to keep the body full of the dirtiest water possible to increase the chances of a protein smacking up against a bubble.

 

[RichConley]

Re: Recirculating skimmers a gimmick????

<a href=showthread.php?s=&postid=8884658#post8884658 target=_blank>Originally posted</a> by college429
I don't understand the function in the design of recirculating skimmers.

The efficiency of skimming is primarily a function of chamber size, dwell time, amount and size of the bubbles, and turn over of the tank, the design of typical recirculating skimmers does not affect any of these.

The short path of the recirculation does not significantly affect dwell time.

Bob Goemans', Ph.D. book Protein Skimming & Activiated Carbon Secrets suggests too much turbulence (bubbles chopped again or colliding at high speed) can actually disloge from the bubbles what we are trying to extract.

Again, I can't understand what this tiny loop of a recirculation could possibly accomplish.

Is this just a gimmick?

(assume ER xx180)
How does a recirculating loop not improve dwell time? We've got a fixed body size, and either 700+ gph from a NW pump moving through it, or 150 gph on the recirculating version. 1/5th of the flow through means 5 time the dwell time.



also, recirculating skimmers are much easier to tune, because flow through and air production aren't linked in that case.

 

[manderx]

and I didn't really agree with Anthony

the more i read from him the less and less i agree with him on much of anything. the perimeter manifolds he recommends that diffuse flow too much and require huge pumps (*much* better to alternate flow between fewer outlets to get stronger blasts). the full-width overflows (within the range we are talking about, the faster you skim the surface the cleaner and cleaner that overflow water will be, so it's not really any better than drawing dirtier water off slower). remineralizing topoff water because it has a low pH (buffering/pH doesn't work like that, buffer/kalk it if you want to use topoff as a vector to add suppliments but don't think that adding DI water with a pH of 6 is going to bring your tank pH down any). and his contempt for RO/DI (DI-only works for some people with some source water, but not everybody, plus RO/DI is cleaner than DI-only).

 

[RichConley]

<a href=showthread.php?s=&postid=8887182#post8887182 target=_blank>Originally posted</a> by college429
Here is another good argument against recirculating skimmers in the following article: http://www.cs.cmu.edu/~cap/raid/skimmers/thoughts/
Quotes:
"The best plumbing arrangement, from the point of view of maximizing efficiency (both measures), would be to pump water directly from the aquarium through the skimmer. After a single pass through the skimmer, the water would drain back to the aquarium..."
"Maximize flow between the aquarium and the skimmer"

Umm, you're proving the opposite point. THat statement says you basically have to have a drain fed skimmer. In a drain fed (recirc) water goes from the tank to the skimmer, back to the tank. In a non recirc, it goes from the tank, into your sump, some of it gets used by the skimmer, but most just gets pumped back to the tank.

 

[sjm817]

Rich, where do you get the 700+ GPH number from?

 

[sjm817]

<a href=showthread.php?s=&postid=8929096#post8929096 target=_blank>Originally posted</a> by RichConley
Umm, you're proving the opposite point. THat statement says you basically have to have a drain fed skimmer. In a drain fed (recirc) water goes from the tank to the skimmer, back to the tank. In a non recirc, it goes from the tank, into your sump, some of it gets used by the skimmer, but most just gets pumped back to the tank.

Few people have ALL of the drain water going through a recirc skimmer although it would be a good idea. In your example of 150 GPH on a recirc feed, if you have a 600 GPH return pump, what happens to the other 450 GPH?

 

[RichConley]

<a href=showthread.php?s=&postid=8929113#post8929113 target=_blank>Originally posted</a> by sjm817
Rich, where do you get the 700+ GPH number from?

The ER 180 has a genX 4100 as the pump. It moves ~1100 gph stock, so probably somewhere in the range of 700 while drawing air with a needlewheel.

As opposed to a recirculating version, which may only move 100gph through the skimmer. Thats way more dwell time.

 

[sjm817]

I would say a lot less. I have an RS250 (Gen-X 6000). I never measured it, but just observing the water flow from the exit it doesn't look anywhere near 700 GPH.

 

[RichConley]

<a href=showthread.php?s=&postid=8929147#post8929147 target=_blank>Originally posted</a> by sjm817
Few people have ALL of the drain water going through a recirc skimmer although it would be a good idea. In your example of 150 GPH on a recirc feed, if you have a 600 GPH return pump, what happens to the other 450 GPH?

It just goes back to the sump and bakc to the tank of course...

The point is, if the contention is that your source water is pretty clean and you want to get the stuff coming out of the skimmer as clean as possible, then recircs win. If you assume your water is dirty, and you're in a "I need to get as much out as quickly as possible before my inhabitants die" mindset, a high throughput skimmer wins.


Think of it like cleaning a floor with a hose, vs cleaning with a toothbrush. The hose will remove the most stuff the quickest, but its never gonna get the scum out of the grout, like a brush can.

It is my oppinion, that if your skimmer isnt sufficiently undersized, you never get to the point where you have to do the hose style cleaning. You're always detailing.

 

[sjm817]

<a href=showthread.php?s=&postid=8929096#post8929096 target=_blank>Originally posted</a> by RichConley
Umm, you're proving the opposite point. THat statement says you basically have to have a drain fed skimmer. In a drain fed (recirc) water goes from the tank to the skimmer, back to the tank. In a non recirc, it goes from the tank, into your sump, some of it gets used by the skimmer, but most just gets pumped back to the tank.

Just wanted make the point that recirc, or non, unless you are feeding 100% of your drain water through the skimmer (which would be ideal), the skimmer process only some of the water. The rest just get pumped back to the display.

 

[RichConley]

<a href=showthread.php?s=&postid=8929264#post8929264 target=_blank>Originally posted</a> by sjm817
Just wanted make the point that recirc, or non, unless you are feeding 100% of your drain water through the skimmer (which would be ideal), the skimmer process only some of the water. The rest just get pumped back to the display.

Right, but where is you pump in your sump? Its under water right? All this stuff we're collecting off the surface with the overflow is just goign to flow right back over that pump, and then back into your return compartment.

 

[sjm817]

<a href=showthread.php?s=&postid=8929285#post8929285 target=_blank>Originally posted</a> by RichConley
Right, but where is you pump in your sump? Its under water right? All this stuff we're collecting off the surface with the overflow is just goign to flow right back over that pump, and then back into your return compartment.

Agree, but that was not the point. Your post implied that a recirc skimmer process all of the drain water and a recirc does not. In most cases, neither does.

 

[college429]

Re: Re: Recirculating skimmers a gimmick????

Re: Re: Recirculating skimmers a gimmick????

<a href=showthread.php?s=&postid=8929067#post8929067 target=_blank>Originally posted</a> by RichConley
(assume ER xx180)
How does a recirculating loop not improve dwell time? We've got a fixed body size, and either 700+ gph from a NW pump moving through it, or 150 gph on the recirculating version. 1/5th of the flow through means 5 time the dwell time.

The dwell time I was referring to was not the dwell time of the water, but the dwell time of individual bubbles. This is what matter more, in my opinion.

 

[college429]

<a href=showthread.php?s=&postid=8929096#post8929096 target=_blank>Originally posted</a> by RichConley
Umm, you're proving the opposite point. THat statement says you basically have to have a drain fed skimmer. In a drain fed (recirc) water goes from the tank to the skimmer, back to the tank. In a non recirc, it goes from the tank, into your sump, some of it gets used by the skimmer, but most just gets pumped back to the tank.

I believe he is describing "one pass" non recirculating. Non recirculating is the point he is trying to make, I believe.

 

[college429]

<a href=showthread.php?s=&postid=8929170#post8929170 target=_blank>Originally posted</a> by RichConley
The ER 180 has a genX 4100 as the pump. It moves ~1100 gph stock, so probably somewhere in the range of 700 while drawing air with a needlewheel.

As opposed to a recirculating version, which may only move 100gph through the skimmer. Thats way more dwell time.

Again, isn't it the dwell time of an individual bubble that is more important than the water. If the dwell time of the bubbles is the same in two skimmers, wouldn't you want to pass more dirtier water by that bubble than cleaner longer dwelling water?

 

[Fishbulb2]

There seems to be at least some debate as to whether or not the ideal is to pass as much water throught he skimmer and maximize concentration or minimize flow through and allow dwell time. I agree with Rich's analogy of the floor scrubbing. That I probably have very low organics in my tank and I really need to maximize the dwell time to get them out unlike a non-recirc. The best thing about recircs, like has been stated by at least half the people on this thread, is that at least you can control that. This is a fickle hobby with popular opinion shifting every week. So if you want a slow flow rate, fine. Just close the recirc inflow valve. There you have it. If you want a fast flow rate, well then just open it. If you believe skimming from the surface is best, well you can do that with a recirc.

With a non recirculating skimmer, you are just stuck. They aren't called plug 'n' play because they work right out of the box. It's called plug 'n' play because if you aren't happy with it, you're screwed. Nothing to adjust. Nothing to mess with.

FB

 

[Fishbulb2]

<a href=showthread.php?s=&postid=8929570#post8929570 target=_blank>Originally posted</a> by college429
Again, isn't it the dwell time of an individual bubble that is more important than the water. If the dwell time of the bubbles is the same in two skimmers, wouldn't you want to pass more dirtier water by that bubble than cleaner longer dwelling water?

I would think it is the dwell time of the organic molecule in the skimmer that is more inportant than the bubble. It does not matter if the protein is eventually sucked in by bubble A, B, or C. It just needs to be in the reaction chamber long enough to finally get associated with any given bubble. This is, of course, just an opinion.

FB

 

[BrokeColoReefer]

My current skimmer is sold and marketed as a recirc skimmer. Its designed to be fed by a feed pump and a second pump is what drives the becketts. Im not sure i would classify that as a recirc skimmer. I can say this, when i had the overflow plummed directly to the skimmer it was hard to control the water level. Once i put it on a feed pump it runs smooth as glass. Basicly i have my feed pump in the sump where the overflows dump into. There is some baffles that seperate the feed chamber from the skimmer output chamber. The third chamber is where the return to the tank goes. I put feed pump (mag 7) that had a higher GPH then the return pump was putting out. So in theroy, all the overflow water should have to go through the skimmer...? Since i dont have water going over the baffle i would supppose this would have to be true.