Thanks for the advice guys,so the fact that my overflows have the potential to drain 2600gph only means they will do this if the return pump is large enough,so with a ehiem pushing 900gph to the tank will the overflow box waterlevel be the same as the main tanks level or less?Will the large diameter bulk-heads quickly drain the water to the point were the pump is unable to return it fast enough giving me a lower water level in my overflow box?