How much flow is enough flow?

[jiminy_crime]

Is there a general rule that is used when your tank has too much or too little flow?

I was just in my LFS and noticed he had a large half moon softie tank with very little to low flow and the tank looked amazing.

Right now I have 1,800 gph coming out of 4 PHs. The reason this issue has come up is I recently bought a rainbow BTA and he has been on the move a lot in this tank and I think the flow may be the reason.

I wonder if I should drop down to 2 PHs at gph of 500.

Any help with this would be greatly appreciated

 

[killagoby]

I've got a RBTA in a 3 foot long 70 gallon tank with one MP40 dialed down to the minimum. Anything more and it shrivels up

 

[CStrickland]

The general rule is whatever prevents settling or cyano and keeps the water oxygenated for fowlr and softies, 40 gph per gallon of DT for mixed tanks, up to over 100x for things like barebottom sps. But flow is more than math, some powerheads are more directional than others, and the aquascape really dictates what each specimen is receiving. Like one monster powerhead at the end of a tank that has 2# of rock per gallon of water is a totally diff animal from several small ones in a minimalist tank.

You can totally mess around with it, you're not going to do any real damage as long as you don't go crazy and turn them all off. That's the only way to get it just right. And then you move one rock and have to start all over