I have a 90 gal. and i run 2 Koralia 3's they seem to be just right. On top of that flow you have the circulation through the sump, i think mine is approx 400gph and then i have a cansiter filter i use for carbon and other medias like a reactor which i would say is flowing about 200 gph. One thing about the Koralia's, if you remove the front grill from it and the bezel that directs the flow you get really good flow in all directions, instead of a massive jet in just one direction.