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I was wondering if fish sleep, or do they just rest and not move ?

Fish rest, not sleep.

Fish do sleep, or at least in a state that is called sleep. Many do not close their eyes. Some fish sleep at a certain type of day/night like we do. While others sleep for short periods of time, multiple times through out the entire day. There have been many studies on this subject, and they all have different findings; from "no" they don't sleep, to "yes" they do, to some do and some don't. So in the end, you will have to determine which you chose to agree with.

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There is always a bigger fish...

I always thought my fish were sleeping. When I turn the light on in the morning they don't seem to be aware of anything around them. They're just floating there for a little bit. I have to wait for them to start moving around to feed them cause they don't seem to see the food when they first "wake up".

rest, bettas for sure will rest in plants when the lights are out.

Depending on your definition of sleep, the answer is usually yes.

Like Acid said, fish don't close their eyes (due to the lack of eye-lids) thus do not sleep like most terrestrial animals do. However, they do go into a sleep-like state.

For a test, most of the time, fish will rush to surface and great you when you come near the tank. However, if you are ever awake when the tank is in the dark and has been for a while, if you turn on the light, you will notice that fish will act very groggy and slow, and will want to hide from the light. Most fish when startled will dart, however, being in the sleep-like state, they are not fully "awake" and will slowly move around.

well i say they do think of it in the way of a reptile lizzards sleep with their eyes shut, while snakes can, sleep too but because of their lack of eyelids they sleep different, thats how i think of it

Studies on both wild and captive dolphins have also revealed a very unique way of sleeping. Like humans, their brains are divided into two hemispheres. These animals have the ability to allow one hemisphere of the brain to sleep while the other half is awake. During sleep, dolphins tested in an aquarium swam mechanically in circles and observation of wild dolphins has shown much the same behaviour. Spinner dolphins, for example, are known to enter shallow waters of protected bays to sleep. These bays are often characterised by white, sandy seabed where the dark shape of a predator such as a shark is more clearly visible. The dolphins swim in circles, presumably with one half of the brain resting, whilst the other half keeps an eye open for danger. What is interesting, and has been shown to occur in birds, is that moving in clockwise followed by anti-clockwise directions allows the animals to alternate which halves of their brains are getting rest – the outward facing side remaining alert to predators whilst the inward facing side sleeps.

From http://www.apexstuff.com/ot/200503/natwon.asp

I have also read the sharks can do the 'turing off half the brain thing.' I am usually up pretty late, long after the fish tanks' lights have gone out and I can certainly tell the the tiger barbs are resting/sleeping. That nose-down posture is virtually unmistakable.

Sharks have a multi-lobed brain, not a 2 hemisphere. So they have an inline brain and not two halves. For this reason they cannot shut down one half. Sharks sleep in two different ways, depending on the shark. Some sharks, like from the dog fish families, actually lay on the bottom and sleep. While the others, that cannot stop swimming, less they suffocate, take quick naps, while falling towards the bottom. They keep their mouths open, stop swimming, and slowly just sink. This keeps the water moving across their gills so they can breath. After "falling" so far, they wake up and work their way to the surface, only to do it again.

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There is always a bigger fish...

Dolphins are not fish, they are mammals...

The question asks if fish sleep, not mammals.

Jorge

I feel bad for the sharks... That's a horrible way to sleep sinking waking up and doing it again. It sounds like some days I used to spend in class. Slowly falling asleep until my head hit the desk waking up siting straight and doing it again to compensate for lack of sleep but it never worked I always ended going home and getting at least 8 hours of sleep.

Yes. As has been pointed out, try looking into your tank JUST as the lights come on, when it's still dark in the room (or not bright, anyway). The fish will be listless, groggy... My bettas are still snuggled into their hidey holes or respective plants.

On the other hand, I've noticed that fish other than bettas (guppies, tetras, danios), don't seem to sleep as much. No matter what time I go to bed (fish lights are on a timer, and so go turn off prior to my going to bed), I can always see those fish moving. I think they must take catnaps in comparison to bettas. Since my bettas always swarm to the front of the tank and say hi, I can tell when they've tucked in for the night.

I've found that even if you turn on the lights and let two normally aggressive bettas see each other late at night (after lights out), they're sluggish and won't even flare at each other, and hardly even look at each other. And trust me, those two ALWAYS flared at each other. They MUST have been sleeping, or at least resting soundly.

I'm curious as to why other fish don't seem to sleep in the same way as bettas do. I mean, no matter what time I look in the tank, I always see the others moving, but I'd have to do some serious attention getting before the bettas would even look at me. *shrugs*

~Meow. Thus spoke the cat.~

The best way to check your own fish out I have found is to wake up early, before the sun is up...take a look at your fish, without turning on the lights or anything else, being quiet about it...take a look in your tank and see...it may take a couple of times to catch them, but you will see that they aren't being your "typical" fish, but just seem to be floating there doing nothing...My students love creeping into the classroom to watch them sleeping first thing in the morning...

Or you might have even noticed that if you are up early and suddenly start making your morning noises and turning on all the lights fast, they will suddenly start darting scared like they had been spooked out of sleeping...

That has only been my experiences, heidi

"I've got a great ambition to die of exhaustion rather than boredom." Thomas Carlyle