Ok now yall got me misunderstanding, when you say flow are you talking about flow from sump and combined flow from any powerheads? or are we talking about just the return flow from the sump? I have the mag 2.5 for the return from my sump (20 gal tank customized with baffles) and then in the 55 gal tank i have 2 maxi 1200's and a seio 820. Wondering now if i have enough flow and if i don't ......... wow how am i gonna keep my corals put with more flow than i have now?????? I can barely keep things put now as it is, lol.