Silentskream, are you refering to the genetically engineered danios that have been infused with the substance that makes jellyfish glow?
i've never heard of that, but you might be correct. they did look an awful lot like my zebra danios, except of course that they were glowing.
i'd like to point out that fish dont have eyelids. so sometimes turning a light on abruptly is not the nicest thing you can do to the little guys.
think of it as you're in a dark room with your eyes open and someone unexpectedly turns on all the lights at the same time *BAM* that just hurts 8(
fortunately for you, you have eyelids. you can close your eyes and try to adjustto the change in light.
fish dont have eyelids, so try to make the change a little gradual, that goes for ANY tank lighting.
i cant imagine that blacklight would be Dangerous, but personally they give me a headache, so they might make the fish somewhat uncomfortable as well. but i dont know if fish get headaches.