sleep for fish

[Sam]

how many hours a night do fish need to be in darkness so they can sleep?

[DR.V]

Hold on, let me ask my fish first ^^

[weird]

That is an interesting question.

Well my fish go into a rest state (day dreaming) about 1 am after the lights have switched off (if I suddenly turn on the light ... they are still alert but they are obviously still determining whether or not there is a threat or can they still rest)

How many hours they need ? Not sure. Do they actually need the light off to go into a resting state ? Not sure either but I know in my case the light off signals to them its rest time. Abit of side trivia, most fish don't have eyelids, except for sharks.

[Merrilyn]

Well that made me think. It is known that dolphins rest with only half their brain asleep at the one time. If their brain were to shut down into sleep mode fully, they would drown. (Yes I know they are mamals and not fish lol) There is some doubt if sharks sleep at all, because they must continue swimming to pump the water over their gills all the time, so they cannot in effect, sleep.

I know when I turn my lights on in the morning, my fish will be resting on the bottom of the tank, and appear to be sleeping, and it will take them quite a few minutes before they become active. So I guess, the answer is, yes, discus do sleep, but maybe not in the form that we know.

As far as how long do they need, I really can't answer that, but I guess 8 or 10 hours seems reasonable.