Warning! Lava Flow in tank.

I think they pretty much ignore it. My last light system I had the dual actinics with the 420/460 spectrum. The 420 kinda looked like a black light.. it was hard to tell that it was on, but that's the way it was suppose to be. From what I read it was just to simulate a broader deep water spectrum... not sure if anything I have actually benefited from it.. it just made the glowing corals pop out more. Now I've got a new light system and the actinics that it came with give off a lighter blue light and they don't get the corals to glow as much. that's why I was curious and started playing around with the black light. I still might mount this black light and turn it on when the lights go out... it's really cool seeing the stuff glow.

 

Reminds me of a day-glo poster!