I do have a UV Filter hooked up, I originally hooked up to help with the Algae problem that I was having. I immediatly saw clearer water in my system and a decrease in algae, but it did not help with the algae a great deal.
But I do have a very heavy bioload.
It and my skimmer are always turned off however for at least 4 hours after I dose with prodibio every two weeks. Otherwise it and skimmer run 24/7