Well a sterilizer will kill indiscriminately. Good things as well as bad things will be affected. Remember in a reef setup, you're striving for biodiversity. The UV sterilizer will definitely go counter to this. In a FOWLR, I see more use for it. However, many copepods, isopods, amphipods will be eliminated which might not be the best course of action either. For water clarity, UV is nice though.