My older son (6 year old) and I are wondering about whether or not our danios are asleep. They are swimming, but very slowly, at this late hour. (We have a night light on, and the 3 glofish are clearly visible but the regular zebras are not, btw.) Do danios swim while asleep or do they lie down at the bottom of the tank? (In which case I don't think I have ever seen a danio that is asleep.) Other option: I once saw a danio swimming in place like on astationary bike, moving her tail, but without moving forward - was she asleep? When I leaned closer for a better look, she rapidly swam away. How often and how long do danios sleep? And if they swim when asleep, how come they can turn around before bumping into stuff like aquarium wall or decoration? I read somewhere that they do not have eyelids, right? So they sleep with eyes open?