Filter flow volume vs turnover

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Aquarium Advice Apprentice
Feb 25, 2008
Moscow, ID
I've read in many places that the current recommendation is 10x turnover in a tank and I've perhaps mistakenly assumed that this meant 10x tank volume through my filter/sump.

I currently have a 40g FO tank with integrated wet/dry filter and have plans to upgrade sometime in the next year to a 72g FOWLR w/20g sump. I measured my current filter return pump at 180gph and was looking at replacing it with a 400gph unit to get that 10x turnover. The LFS said that the 10x is for tank turnover and not meant to mean that much through my filter and pointed me in the direction of a Koralia 1 to get the additional turnover.

1) Is the LFS right when they say wet/dry filters need lower volume and I should just add to my tank turnover with the Koralia 1?
2) Does this change with the use of a sump instead of a wet/dry and the full 10x should go through the sump?
The LFS is correct. 10x-20x turnover is factored by return flow and powerheads. If Macroalgae is kept in the sump a mellow flow is ideal as well as it allows the macroalgae more time to do its thing. A sump or wet/dry filter isn't even totally necessary its possible to be successfull with just powerheads and live rock in the tank.
:silly:I had the same misunderstanding. Thank you for clarifying that. So I should be ok with a 700gph pump with a 72 gallon tank, I will just get the power head to supplement.
Still lost, but seeing the light.:confused:
Yes! The return pumps must not pump more water than the overflow can drain. The two should be matched. The overlfow for a 72 will be about 600 gph, so you want a return pump that produces up to or slightly under 600 gph at the height of the return pipe outflow (head height). Every bend in the pipe from the return pump to the return outlflow will also reduce the gph slightly.

If your return tank is under your tank and the distance up to the topof the tank is 4 feet then you want a pump with rated capacity of 600 gph at 4' head height. The pump will probably have a rated capacity of around 900 gph at 0' feet. For instance the Mag 7 is rated at 700gph at 0' and 450 gph at 4', while the Mag 9.5 is rated at 95-gph at 0' and 800 gph at 4'.
So for my current setup, I will have about 50% of my turnover going through my wet/dry. Should it be the same percentage when I switch to a sump w/LR (i.e. 450gph through the sump for a 72g tank + 20g sump)?

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So for my current setup, I will have about 50% of my turnover going through my wet/dry. Should it be the same percentage when I switch to a sump w/LR (i.e. 450gph through the sump for a 72g tank + 20g sump)?

It doesn't really make a huge difference what percentage of flow goes threw the sump the goal is 10x-20x of flow in the main display. Sumps are for hiding equipment mainly the return pump is just another way to equate for flow in your main display. If your sump has a refugium zone then a slower flow threw that zone is ideal. But a fast flow in the refugium really has no ill effect either. Just make sure the Overflow is rated to match up with the return pump and that your flow is at least 10x turnover. Some people have 35x or more turnover rate and swear by it. Too much flow is not really a problem unless the fish have difficulty swimming and the substrate turns into a sand storm.
I have less than 5X turnover in all my tanks. Water is crystal clear and the fish are thriving. Keep in mine that fish need calm water to rest. Some tanks are whirlpools and the fish must swim 24 hrs/day to keep from getting stuck to the filter input tube.

The key is maintaining healthy bacteria. Excess water flow does not necessarily improve bacteria growth. In fact, high current sends fish waste, driftwood pieces, and sand flying around which contributes to the clogging of the bio-media pores in the filters. It is better to let the crud fall on the substrate and vacuum it off during the water changes.

BTW - 5 X was the "standard" for a while. It went up to 10 X last year. I see the previous post mentions 35 X. I guess that will be the new standard in a couple years.
I take it you have a FW tank which would make sense to have only have 5x turnover.
Reef tanks filled with LR and sps coral need much greater flow. There are still plenty of places between the rocks that have lower flow and the fish sleep quite well in those areas. The standard of 10x - 20x has around for at least the last 4-5 years. The higher numbers are just getting talked about now. They might well become the standard if it is found that reef tanks do better with higher flow. The wide flow power heads have only recently become popular. They too are having an impact on how much flow is needed.
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