Where to put the power heads is a question thats been around a long time. There is no exact one way method to do it, just some guide lines of which here a a few: Power heads should not produce a lenear flow at the corals but should create a caotic circulation. This can be accomplished by placing power heads opposing each other. many cirulation plans can be modified by using different sized pumps, wave makers, large diffused water movers, and so forth. Typically I like to put the two large pumps in the corners pointed to the front center of the tank at the surface, and the others I like to arrange to give good water movement throughout the system. You do not want water flow to beat directly on your rock or corals but just past um so that the water around them is moving in all areas. I hope this helps and is assumed your pumps are at the top of the water collum. I have also fitted some half inch 45% pvc fittings over the ends of the outputs to direct the water lower into the system and used what i call a duck bill disperser (wide flat with slit to give a sweeping dispersion. good luck. im sure others will weigh in here also.