If fish sleep, what time do they sleep?

Answer 1

Some (zebrafish) and maybe all fish do sleep, they have a 24 hour diurnal circadian rhythm just like us. This means that during the evening (or when the lights are out) they are in a sleep state and do not move much. If you feed them at night when they are trying to sleep, their activity will slow down in the daytime because they are sleep deprived!

Also, they have and respond to the sleep hormone of darkness melatonin.

See the referenced article, sleeping zebrafish have been observed scientifically and there are published scientific papers on this. Got to pubmed.gov and type in sleep and zebrafish.

Here is the person who discovered this:
Irina Zhdanova proved that melatonin does in fact promote sleep in zebrafish and that it somehow affects several tissues at once, slowing down the heart and lowering body temperature

Answer 2

We tried an experiment when we were in school. If you fed the fish at times when the lights were switched off, they'd actually be less active when the lights were on.

As long as you have a constant and regular timing, the fish learn when to wake up and when to sleep.

However, fish which have their tanks lit for too long each day, we discovered, lose their fertility over time and many become sterile, probably because they can't really get proper sleep since they have no eyelids to shut the lights out.

So the answer to your question, is, Anytime when the lights are off and they know they're not going to get more food until the light goes on again.

Answer 3

Fish, like all creatures have an internal body clock, called circadian rhythm. Even if the fish tank lights are on 24/7, you would find every day at a certain time, when you walk past the tank, the sleeping fish will be sitting still on the bottom resting.

Answer 4

It's probable that fish do sleep in some form, whether slowing down or coming to a complete stop, whether hiding or doing it right in the open. Most fish "sleep" in the day and are active at night. But when they sleep the slightest ripple in the water will disturb them. Nevertheless, in some way they rest, just as we do.

Answer 5

fish go into something called "suspended animation" I know it sounds like something from star trek but they do. It is kind of like a meditation state I think would be the only way of describing it. It tends to be at night when the lights are off or low, but it can be anytime. This is why it is very important not to turn bright lights on in a room with fish at night, once they have already been turned off. It frightens the fish and they can injure themselves by swimming scared into the glass or other objects.

Answer 6

not so much sleep as in a deep relaxed state, get up really early one morning and switch the tank light on most will be slow and sluggish at the bottom of your tank.

Answer 7

I had small aquarium in my house .. i hv noticed that they just stand still in one place when the lights are off!! i think in that time they will be sleeping with eyes open!!

Answer 8

fish do not sleep the only thing it does is to stop his moviment to relax his body even his eyes do not close

Answer 9

fish dont got eye lids like we do they sleep any time.

Answer 10

My goldfish sleep at night.