Lol in a 20 gallon right? :P
Anyway. I am not sure who told you 750 is not enough :S Because to be honest, I would say that's too much; not for the tank but from one single power head.
My tank has lots of movement (500gph + 120gph + 240 gph + 425 gph) but from different sources to create an alternating flow. That's something you want (makes coral flow look better too). Why not get two different power head of 425gph or something
