What I am using now is a koralia 4 (1200gph) and a seio 620 with a 1200 gph return pump, so 2 6045s would have to be better, wouldn't they? Same flow as the koralia, takes up less space, and then twice the flow as the seio if I replaced the two. I would like something so that my corals don't grow all in one direction such as my birdsnest grows all to the left and doesn't look natural, but the controllable pumps are real expensive.