It helps keep the rock clean and spread coralline better but I agree with Atari. An alternative method is point or angle the powerhead towards the glass so it "rebounds" back at the rock surfaces. This will difuse the flow and accomplish the same goal. Corals will get a less luminar flow and the rock will get a helping hand as well. You can also aim the powerheads so they "X" streams giving the flow a more choatic rhythm.TygGer said:Is it correct that powerheads should not be aimed directly at LR?