It really depends on the lighting requirments of the coral. More light, put it high, less light put it low. Be care about placing coral directly on the substrate. I have a trumpet coral that was very happy resting on my LS
until my pistol shrimp dug under it casuing the bottom 1/3 to be burried in the sand. I did not notice this right away and part of it died. i feel terrible. Now I do not have any corals on the substrate.