Do tropical fish sleep?
Because fish live in water and their eyes are always wet, they don’t need to blink and have no eyelids. So you will never see a fish with its eyes closed – but yes, they do sleep. Most fish are diurnal (active during the day) and at night will find a quiet spot in a corner or hidden behind something. They will stop moving and their fin movement will slow or stop altogether. Their breathing rate slows down and their eyes do not flicker from side to side. They are asleep. Fish are light sleepers and wake easily, but will panic if woken suddenly, which is why you should avoid turning on the lights when the room is still dark – turn the room lights on or open the curtains first as a sudden transition from ‘night’ to ‘day’ is very stressful.
