2 things. One, I actually enjoy watching the tank when the lights are off as much, if not more so than when the lights are on (all lights are off by 6 pm). 2 I litterally can't even put a pipette in the water when all the critters are out. The hippo tang grabs at it, and has pulled it out of my hand on occasion. My big mouthed six spot goby grabs the end of the pipette and waits for me to squirt mysis right down his throat. And don't even get me started on the cleaner shrimp... I like seeing it under the moon lights as much as under the MHs. I do know, however, and have read, that they can be trained to open during the day. I figure, its happy now, and i'm happy, so why change it?