Yet Another Water Flow Question

[Dave Clark]

So I've been Googling and I can't really find a general consensus about this, probably because there are variables and differing opinions etc., but I'll ask anyway.

Say I have a tank of "X" gallons with a typical amount of live rock.

How much flow should I have *through my filter system* if I have just softies? If I have LPS? If I have SPS?

How much *total water flow in my tank* (eg powerheads/wavemakers, in addition to my return pump) should I have if I have just softies? If I have LPS? If I have SPS?

I recognize that in smaller tanks, one might choose to have all water flow via the return pump, with RFGs or whatever.

Thanks!

 

[stinkydavis]

5-10x turnover for return pump. 100 gallon tank= 500-1000gph return pump. 25-50x turnover in tank. Calculate with return pumps flow figured in. Softies and lps on the lower end so 25-35 Sps can be 40-70x turnover

 

[Dave Clark]

5-10x turnover for return pump. 100 gallon tank= 500-1000gph return pump. 25-50x turnover in tank. Calculate with return pumps flow figured in. Softies and lps on the lower end so 25-35 Sps can be 40-70x turnover

Thank you. So I've actually seen a lot of articles saying that 20x should be the target for the return pump. Thoughts?

 

[Mschmidt]

My understanding is 4-6x through the filter. 20x won't give enough contact time with the bacteria in the sump. but if the rock in the tank is adequate, probably enough contact time there for ammonia processing.

I like stinkydavis' recs for flow. I was told 10x, but that is too low.

 

[thomas_neil]

I think return pump flow is really dependent on the size tank. 10x is easy on lets say a 100 gallon tank, but on a 400 gallon tank your goal would be lower. I'm planning on a roughly 5x turn over in my sump for my 300 build. Might drop it lower if the fleece roller cant keep up with the flow.

I'm a believer that if you push water to fast through a sump it doesn't give the skimmer/ fuge/ any thing else in the sump time to do what its in there to do.

 

[PotatoPig]

Thank you. So I've actually seen a lot of articles saying that 20x should be the target for the return pump. Thoughts?

This really depends what you’re trying to do with your sump. IMO 20x is very high. I have a 75 gallon and can’t imagine trying to put 1500gph through the sump.

Most of the time it’s around 3-4x. This seems to work - filter socks filter, skimmer skims, ATO ATOs, refugium refuges, reactors react, heaters heat.

Much more than that and the return line would dump a lot of flow where I don’t really want it and would then have to manage.

 

[00W]

Flow inside the tank is different than return pump flow through your filter IMO.
I have a 75 and run maybe 200 gph through my sump.
Skimmer works better, water is clearer, socks work better, tank looks better, etc than when I ran 5 times through the filter, which I did for years.
Flow inside the tank is super high.
Just my opinion and every tank is different.

 

[RocketEngineer]

Ignore the numbers, What are you doing with each kind of flow?

Sump/return: You want the water in the display to have nearly the same parameters as what’s in the sump. I say nearly because the equipment in the sump will be changing something. The goal is to keep the two close enough that the display is within the target range.

Flow in the display: to promote exchange at the surfaces. This could be gas exchange on the top of the tank, chemical exchange at the coral surface, or food/waste transport. Without enough flow, solids settle out and gas exchange isn’t effective. Too much and corals can’t feed and those not used to high flow can get damaged. Also, flow can be currents or waves. Some critters love currents, others waves.

I’ve seen sumps down in the 1.5X realm and internal flow over 50X. Ignore the numbers and understand the reasoning behind flow.

 

[Dave Clark]

Ignore the numbers, What are you doing with each kind of flow?

Sump/return: You want the water in the display to have nearly the same parameters as what’s in the sump. I say nearly because the equipment in the sump will be changing something. The goal is to keep the two close enough that the display is within the target range.

Flow in the display: to promote exchange at the surfaces. This could be gas exchange on the top of the tank, chemical exchange at the coral surface, or food/waste transport. Without enough flow, solids settle out and gas exchange isn’t effective. Too much and corals can’t feed and those not used to high flow can get damaged. Also, flow can be currents or waves. Some critters love currents, others waves.

I’ve seen sumps down in the 1.5X realm and internal flow over 50X. Ignore the numbers and understand the reasoning behind flow.

Understood. I believe I am oriented towards understanding the reasoning behind the flow, which is why I asked about how display flow might depend on the corals one is keeping.

Re sump flow; in my case, I have a nano AIO, and I'm passing water through my filter material (floss and carbon) at about 20x the tank volume. I currently have only the return pump for moving water. I'm considering adding a powerhead because (1) I've read articles that have suggested I drop my return pump flow to about 10x, and (2) I'm thinking that if I add a powerhead to the opposite side of the tank, the display flow might be more randomized (correct word? turbulent?).

 

[stinkydavis]

If you are running softies you can run run just the return pump and most LPs. If you are getting torch corals or the longer end tentacles on lps I would say you may want I very small power head. On Sps you are going to want one. AIO don’t really need the contact time as normal sumps and you can just run the return pump wide open.
A 32gallon biocube with one AI Nero and the return pump would be plenty for almost anything you put in there.
Truly don’t focus on the number to hard. Flow is important but not as important as good parameters and good lighting.

 

[RocketEngineer]

If you are running softies you can run run just the return pump and most LPs. If you are getting torch corals or the longer end tentacles on lps I would say you may want I very small power head. On Sps you are going to want one. AIO don’t really need the contact time as normal sumps and you can just run the return pump wide open.
A 32gallon biocube with one AI Nero and the return pump would be plenty for almost anything you put in there.
Truly don’t focus on the number to hard. Flow is important but not as important as good parameters and good lighting.

The only piece of equipment that hobbyists use that requires consideration for “contact time” are our UV sterilizers. Otherwise it’s a multiple pass filtration system, time isn't a factor.

 

[stinkydavis]

The only piece of equipment that hobbyists use that requires consideration for “contact time” are our UV sterilizers. Otherwise it’s a multiple pass filtration system, time isn't a factor.

as a hobbyist I disagree and believe that flow through your fuge is important to be slow enough to allow contact time with you macro algae and alwoy detritus to settle before going back to the display. But I am just trying to give the OP a straight answer instead of an overwritten knowledge dump that alot of newer hobbyists have trouble digesting.