Good question! lol Since mine is predrilled already I will be going for 600 gph
. My 125g goes at 1200 gph
or so for comparison. BUT my 125g is also a reef tank so I wanted alot of flow.
I plan on adding 2 koralia powerheads at 750gph as well. Hopefully that will be enough. I don't have the money for a new set of 1050 gph
powerheads and I have the 750's doing nothing so in they go. lol