Well, many of us have at least once had an aquarium and since we saw that fish were swimming around all the time, almost without stopping nor even wink at all, we wondered if they ever slept or what. Besides they keep their eyes open all the time. So, do they sleep? And if so, do fish do so with their eyes gape open?
Firstly, they do not have eyelids as they don't need to wink as they live in the water, taking into account that the main reason why living creatures wink is to moisture their eyes. Most of the times we don't notice but fish are sleeping when lying at the bottom of the aquarium and they are not moving whatsoever, even if their eyes are open they're sleeping.
