I have a 75g reef, and i'm beginning to notice some dead areas in the tank. I have 2 maxijet 1200's now, but i'm about to rearrange them and add a SEIO powerhead. My question is which sized SEIO should i get? I noticed they come in flow rates, 620.820,1100, 1500, 2600gph. I may go ahead and order 2, but i was just wondering which size i should get?? thanks guys