Loaches Online Forum

Folks,
The rule of thumb for filtration is that all the water in the system should go through the filter about every hour, yes? I.E. a 100Gal tank should have a filter/pump that runs about 100GPH?

Certainly there is going to be flexibility with stock-load, species, plants, footprint, sunshine, flow and volume, but as a general is that correct?
Or is it slower or faster?
10x per day?

Thanks,
A

That sounds about right as a minimum. This is an instance where more is better in my opinion.

I think 4x is usually the minimum.

per day or per hour?

I set up my tanks with 10x per hour, based on the manufacturer's labeling. We all know the claims on the box are not usually the actual flow rate, though, so I feel I am getting at the very least 5x per hour, and hopefully more.

River tanks are set up with at least 20x per hour, and I did modify the Aquaclear power head. Yes, this REALLY increases the flow.

Here is a rundown on what the manufacturer's labels say about my 125 gallon tank:
Koralia 4: 1200 gph
Fluval 404: 340 gph
Sump: 300 gph @ 4' head.
Aquaclear 110 power head: 935 gph.

total (in theory!): 2775 gph.
divide by 125 = 22.2 times per hour.
I KNOW there is nothing LIKE that much water movement in the tank!! I could believe half of that, though.

Other indicators of good water movement:
Plants are gently waving.
Surface has small ripples.
Fish swim willingly into the lower parts of the tank.
Fish do not gulp air at the surface more than is normal for the species. (Some Loaches, Cats, and a few others do this naturally, but they take a quick gulp and dive back to the lower area of the tank)

Indicators of too much water movement:
Plants are shredded by the current.
All the fish are riding surfboards.

Indicators of too little water movement:
Water has little oxygen, especially in the lower areas. Fish hang around at the surface, and gulp air.
Snails climb the walls of the tank to get into the better oxygenated areas.
Surface of the water has no movement, and may develop an oily or foamy scum.
Ammonia rising because the nitrifying bacteria are dying of oxygen starvation.