Hi Jinx what Leslie said is correct but you must understand that white spot is a pathogen and what sits in your live rock does not die only what passes through will die,but the down side to a uv is that it kills all bad bacteria aswell as good,if i got to run it i will only use it 1-2twice a week for 8 hours or so but i found by using a 500lt pump it works well,i do not think that there is any proof on what goodness there is or am i totally wrong,the reef masters will have more to say on this post