I would not aim the powerheads directly at any of the corals. You could aim them towards the front glass, or, you could aim them directly at each other behind all of your rockwork. I have ample spacing behind my rockwork to allow for free flow of alot of water, and I have my Koralia #4s in the back facing each other. I have my return forward facing so it crashes the front glass. You want turbulent, random flow. Some corals will need time to get used to it, but if after a few days they seem retracted, I would move the coral to a better suited spot.