powerhead q

[stealthbimmer]

is there a rule of thumb for gph of a powerhead? I am looking to put a koralia in my 20g and 75g, but not sure which size..

[Toddrtrex]

Depends on what you are keeping ( or plan on keeping ) in the tank.

[papagimp]

I've got 2 koralia #2's and a #1 in my 75g. Not enough flow, I"m fixin' to swap the #2's for a couple #3's and get a second #1.

In my 55g leather softie tank, aside from the mag3 return pump, I just have a couple koralia #1's. It's lower flow than i like but for the livestock/coral selection it works nicely. I'll still probably wind up getting 1 or 2 more of the #1's though.

but as for general rule of thumbs, for a reef tank, somewhere around 20-40 x turnover. This includes all powerheads and return pumps/circulation pumps. don't count the skimmer or HOB filters for this (at least I don't) For soft corals/leathers you can usually keep it to the lower end of this, but several variables can change that, while those with sps gardens can have 40 or more x turnover rates going.

for a 20g, your looking between 400-800+ total gph. I will say this though, a 400 gph Koralia #1 is not going to be sufficient, the flow is a very nice non laminar spread out dispersal but with limited distance, a couple would be the minimum I'd try.