Input on low-flow sump

[blabay]

Will be ordering a return pump for a new 54g reef tank and wanted opinions on low flow. Jeff @ reef Dynamics says low flow is much better for skimmer efficiency and it makes sense to me. I rarely see this though. Most of you seem to be running a hi flow sump. I assume this is to maximize water movement in DT. If power heads can do the same thing then why not utilize low-flow?

 

[tdileo]

People use high flow because they don't want detritus to settle. I have a low flow sump and have no issues. I have an emerald, some hermits, and any whelks i find in the DT down there to take care of food and whatever they don't get I siphon out during water changes

 

[293482398]

I think low-flow is actually somewhat common, say 4x turnover rather than 10x or 20x turnover.

The big *gotcha* I think is that manufacturers ratings for their pumps are very generous. Once people use flow meters, they are seeing their flow rates way below the rated value. According to the pump specs for my return with no head pressure, I'm close to 10x, using their charts for head pressure, I'm at 6.5x, but I wouldn't be surprised if it's really around 4-5x.

 

[Robthorn]

I run a Coralvue rodc5500 on my 250g dd. I think it is rated for just under 1600gph.

I do have to run a jebao rw8 in my sump to keep the top of the water from getting nasty in my sump.
Not sure the skimmer is more efficient. Not sure that makes sense to me. If you are providing the skimmer with less nasty water by recirculating the same water through theskimmer multiple times there is less nasty in the skimmer to pull out. No fact or proof here just a quick thought.

 

[mcarroll]

Will be ordering a return pump for a new 54g reef tank and wanted opinions on low flow. Jeff @ reef Dynamics says low flow is much better for skimmer efficiency and it makes sense to me. I rarely see this though. Most of you seem to be running a hi flow sump. I assume this is to maximize water movement in DT. If power heads can do the same thing then why not utilize low-flow?

No offense to anyone's reefing style, but if those are the sumps you're looking for then you're just looking at the wrong people.

2x - 4x is a fairly well-established range for return flow that happens to dovetail perfectly with the throughput of most "properly oversized" skimmers.

Rates >5x are overkill, usually just giving you a bigger power bill and more expensive pump, but also sometimes causing noise and bubble issues.

Rates >10x are from pre-powerhead days.

Buy a properly sized flow pump to get anywhere between 110 and 220 GPH into your tank. Use the manufacturer's flow curve to figure that out.

For a good baseline, a Lifegard QuietOne 1200 or 2200 would do it for a normal tank, and would only cost between $20 and $50. Excellent warranty and you can afford to have a backup on-site. (Redundancy is a good idea for the return pump.) Of course there are many other great options, but that gives you an idea of what to target. :) (It's probably what I'd pick myself too.)

If you're doing anything fancy with the plumbing it could be worth looking at a headloss calculator before you look at the flow curve, but I'm guessing this is not the case now.

 

[Rick's Reef]

Thanks @mcarroll for sharing some details on the different values.

I had a bit of a concern on my new build. I had a return with a 1.5" bulkhead out of my synergy reef overflow going through a 2" Apex flow meter and then down to 1" into the sump for various reasons. However, the fittings were leaking so I replaced the 2" flow meter with a 1" that I had. My concern is while I could sustain 700gph through the 2" FM, the 1" I am only getting about 550gph.

But on a 150g tank, this still gives me a 3.7x turn-over and I am getting much less flow noise through the overflow. So I think I am happier with this setup but I was really concerned with such a drop in flow. In the tank I do have 2 MP40's so I expect overall I am perfectly fine. Thanks for sharing your numbers. I feel more at ease now.

 

[theMeat]

The logic is the gph your skimmer can process should match your return pumps gph.
Have to say have been running about 4x display for many years, and find it much better than the 10x I did for decades before. Less heat and noise, more time for skimmer and macros to do their thing

The trend was 10x display for a looong time. Now the lower 3-6x is finally catching on. 2x is IMO is too low and have had problems in tanks that were that low. One tank was a 200 gal with plenty of flow via circ pumps, with 90 gal fuge, 40 gal sump, and a big butt reef octopus skimmer. This tank should have been doing awesome. Guess the return pump couldn’t hold up to the head pressure of the sump being on the floor below in the basement because within about 9 months the return pumps flow was reduced greatly. Noticed the problem but didn’t feel like replacing a new pump so rode it out figuring the huge fuge and skimmer would compensate. It didn’t. Added circ pump to fuge, gave it a few months, did nothing. Added another circ pump to fuge still nothing. The tank started to have algae problems so I took circ pumps out of fuge, upgraded to a hi head pump which got the flow back around 4x and problem solved. First the fuge cleared up of hair algae, then the macros grew better because they weren’t coved in hair algae no film on the surface. The rocks in display started to clear up shortly after.
Many reputable companies, like Triton and Red Sea max, that have found proven successful methods still recommend and design their product around the 10x way of thinking. Just goes to show you there’s more than one way to skin this cat.