Hey Honda, I have never used one, mainly because I've always had a reef and heard that they really weren't good to use on one. Don't know if that's true or not though.
First ever aquarium 8 years ago was my 135 tall, never even had a freshwater tank, and I went reef right off the bat. I just thought that a UV
sterilizer would strip beneficial stuff out of the water, having corals.
I think with fish-only systems that it would be beneficial though.
I'd like to see what the consensus is on this topic.