I am not sure the position to place my power head. I was told it should ripple the water. I have a 55 g fish only. I just got some new rock and I have noticed the coralline dying. LFS brought them when they did a water change so not sure if the were in or out of water. Just wondering if the flow has anything to do with it. 2 damsels, 2 Nemo clowns ( don’t know the spelling of proper name) red hawk, 2 cleaner shrimp and a few crabs.