I've used a UV on all 3 of my Reefs since their inception. Every coral, clam, shroom, shrimp.... has spawned in every one of my tanks. UV will NOT cause any issues with a reef, except for killing the spawn in the water column. I even had the rare event of an Astrea snail mass spawning occur in my initial reef tank.
UV's kill and clean lots of issues in the tank, dependent on UV exposure time, all free swimming parasites (including ich), all algae in the water column... so you dont get algae outbreaks. You end up with a cleaner environment for your inhabitants.