Some of my fish go into such deep sleeps that I freak out, thinking they're dead. Yeah, if you really want to know, just leave all of the lights off at night for a couple of hours, then come back upstairs (or wherever) and flip on the lights. Odds are they'll be in their hides sleep, or just acting very sluggishly as they move around. Some people've noticed their fish almost seem to get blinded, like people do if they wake up at night and go turn on a light for whatever reason. I'll say with great belief that YES, fish sleep ^_^ And it's the cutest thing ever to see.
Speaking of which... Nina gave me a HUGE scare this morning.
I went to feed her this morning before work, and she was floating near the top, and some of her color was gone... nothing I did would get her to move, until I pushed her with my index finger and she drifted for a second... finally realized I pushed her and freaked out. gained all of her color back and then some. She didn't seem happy with me. Girl's gotta stop playing dead, she almost gave me a heart attack!
Well, fish don't have eyelids, they doen't exactly "sleep" but they enter a resting period in which the fish either floats motionally or lies on the ground.
IMO/E Bettas usually do the floating because it is much easier to reach the water's surface. This is achieved through the swim bladder, it allows them to stop all body and gill movement, which seems like they r dead.
Yeah they sleep, fish do go night night to. LoL but yeah if I turn on my kitchen light which shines a little light in my living room I can see in the tank a little and the clown loaches and red tail sharks will just be laying on there belly on the drift wood. You see them all over the tank just laying on drift wood. And my bettas, they sleep. One of them has one of those floating betta log things, and he will lay in it with his belly touching and he only moves his Pectorals every now an again. The others betta I find sleeping will go under the Indian almond leaves that are on the floor of his tank, and be sleeping on the bottom under IAL leaves. The 2 fish talked about above are males, now I have a female that will lay up in one of her plants and sit there and rest every now an then during the day and she sleeps in the plant at night. The females will jump up as soon as I walk into the room the males will sit there and not move like there passed out, then if I tap the tank they will wake up.