The GPH nomenclature is somewhat misleading, though. 3000GPH of flow is not always 3000GPH of flow. For example, if I put a Vortech on the side of my tank, at 3000GPH, it would create more flow than two 1500GPH powerheads/pumps which were pointed diagonally and deflected off the glass.
I think that random current is more important than actual flow (as it creates movement as well, but just a different type of movement), but I don't think we've mastered how to do this just yet.
Just my $0.02
