Although they don’t gave eye lids, they do sleep. Watch the your fishes in the dark and notice that most of then stay very still and in the same position in the water column by small twitches with their fins. Nocturnal fishes like clown loaches will scurry around at the bottom, looking for any left over morsels of food.
Because fish have no eyelids, it is important that the lighting period reflect what happens in nature. It also gives nocturnal fishes the opportunity to come out of cover.
