I've had a UV sterilizer hooked up to my tank since day 1. Frankly, it doesn't seem to help on ich.

My fishes still get ich or something that looks like ich, every now and then and the strange thing is that since I stopped worrying about it, they seem to shake it off (especially on the blue tang, brown tang and purple) by themselves, usually within days.

The only caveat is that I don't seem to be able to keep powder tangs. Strange thing is that they seem to survive well (eat well) for one to two months, suddenly get ich and die AND pass the ich on to the other tangs in the tank. I love powder tangs but will NEVER ever buy another.