Thanks, I thought as much. I went back trying to find the bit I read, but I couldn't... I did find a few references about not to use a UV sterilizer while the tank is cycling, which makes more sense.All i can comment on is my own experience, and i never had a problem with it.
The beneficial bacterial is in the filter media mostly and the gravel. The UV sterilizer is meant to kill freeborn algae and parasites, etc.
What's the info you have read for why it would effect it?