My tank is the 72 bow. I decided to aim the powerheads at the front glass and use the bow to create random flow. With the powerheads running, flow in my tank is muti-directional, and I have had good luck with it. To the question by scottyh about having powerheads blowing lengthwise, in my opinion for my tank, randomized multi-directional flow is best created by multiple powerheads (one in each corner on the back glass) aimed at the front glass.