in my 65 I have two hydor 1500's mounted on the back pane of glass@ 2 1/2 -3 inches below the surface pointed at the middle of the front pane and the return from my sump is aimed at an intersecting angle about midstream of the hydors, the 1500's are a bit much on the 65 but I got them on sale and they'll be good whenni upgrade to a larger tank "someday" but I think my next purchase will be the wavemaker controller so I can tame my flow a bit