Sati
Aquarium Advice Addict
My fish do that when they sleep apparently. Every morning I turn the light on for my tank my fishy's colors are very muted. Within a minute or two their color is back and bright as ever. I think they must blend into their darker surrounding for a sort of camouflage at night. It's nothing I'm worried about. They do this every day. I've also noticed that they do this when I first bring them home from lfs and they are stressed. I just wondered if many of you have noticed this in your fish as well :]