Do fish sleep?

I'm almost postive the answer is no. But I'm not 100% sure about that mine are always active too.

They don't sleep, but they rest. Particularly at night when the temperature drops if they aren't nocturnal. If I turn the lights on in the wee hours, I scope out my fish, which seem a bit dazed and drowsy until they adjust to the light. Maybe it's just my fish?

I like the way they look in "hibernate" mode. They lose their color and look all dopey.

Depends on the definition of sleep. Check this out directly from NOAA.
http://www.nefsc.noaa.gov/faq/fishfaq1.html
go to the bottom of the page.

My goldies do sleep between the plants. They go to "bed" around 3PM and some of them sleep head down, butt up. The Cardinal Tetras only sleep if I turn the lights off.

yes fish sleep, if you consider a period of low activity, lowered metabolic rate and rest, sleep. they don't have eye lids to close so most people think they don't sleep. but there are definitely "sleep" cycles which fish go through everyday. in fact some fish build mucous sacs to sleep in which blocks their scent from potential predators while sleeping. and some of these fish sleep so deeply that a human can actually handle the wild fish without waking it.

my six line wrasse in fact makes a mucous sac to sleep in everynight in his little hidey hole. even sharks sleep though many have to swim while sleeping to prevent themselves from sinking.

Of course they sleep.

Fish definitely sleep. If you look at them with a slight ambient light at night you'll see them hovering in place. Sometimes if you turn the lights on early it'll take them a few moments to start acting normal again. Nocturnal fish are an exception to this of course, some of my corys sleep during the day, spending extended amounts of time resting in one place. I know they are resting because I've reached in the tank and touched them before they'd bolt off.

http://en.wikipedia.org/wiki/Sleep_(non-human)#Sleep_in_fish_and_reptiles

I suspect it is unihemispheric sleep in fish that apear not to sleep.

My GBR and EBR always look active but my neon tetras get really pale when the lights go out (so i always assume they are sleeping). But they are always moving around, probably just resting.