I did run a UV when I had an ich outbreak, and I do believe it helped in wiping out any free floating parasites.
They also help in ridding nuissance algaes, they can actually make your water cleaner.
However I took mine off when it seemed my pod population was decreasing, and that seemed to turn around as soon as I did.
Right now after my swap, and disturbing my sand bed, I'm going through a mini cycle, and suddenly have film algae.
I may put my UV back on for a short spell to help take care of that, but once that has settled I'll take it back off as I have a mandarin pair that need pods, and that is my only reason for removing it, that and you shouldn't need it after time.
There's a fine line between owning your tank, and having your tank own you!_________________________________________
120G SCA starfire, tunze 1073.02 return pump, Geisemann reflexx 4xT5, 2x panorama pro LED strips, 2x Vortech MP 20's, 40g sump w/ fuge.