Why fish didn't close thier eyes when they sleep?

I don't think they do. I often watch my fish and it doesn't seem like he does. I've purposefully turns out most of the lights and watched him get in his sleeping position. This involves him hiding in between these little trees in his tank. And it appears that his eyes never close. And what's weird is when he takes a drink of water. He goes to the top of to take a sip, lol. Why not just open his mouth in the middle of the tank? Weird.

I think they are affraid of black!

When we go to sleep we close our eyes because otherwise we would have to keep blinking to moisten our eyes. If we were to keep them open our eyes would dry out. Being in a fish tank, the sea or an ocean I don't see that happening so they do not need to close their eyes . Well, seriously, I think it's for survival. They keep their eyes open and monitor the world around them and if something comes along that might harm them their brain detects it and wakens them. Just a thought though, it might be just as false or true as my joke above!

I actually don't close my eyes all the way when i sleep. I can actually fall asleep with them half open. Its kind of weird to be able to do that.

hehehe, nice question.. Well maybe its because they don't have eyelid, we human close our eyes because we have an eyelid, also maybe same as the animals..But i am not pretty sure about that, i just guess.. Hehehe

I find fishes intelligent. They don't close their eyes when sleeping because they're afraid that some other creatures might eat them.... they're doing this for safety purposes. And who knows, closing their eyes might dehydrate their eyes. Haha, just my two cents.

This is one tough question. Fish didn't close their eyes while sleeping maybe because they are afraid that somebody will caught them and when they open their eyes they will be facing the fire or the frying fan, hehehe,lol.

cause they don't have eyebrows to close it

maybe fishes want to forever show-off their pretty eyeballs. hehe. seriously though, fishes don't have eyelids that's why. =)