Yes, lots of sand and rock. I work 2nd shift so I see everyone from morning to afternoon. Then again late at night with the moon lights. The PJ and Shrimps are always active. Maybe the coffee pot is to close to the tank.
Actually, I think fishes do not have eye lids so they cannot turn off the eye inputs but their brains may be able to turn off the eye input and allow the fishes to sleep. This is just like our other four senses, it cannot be turn off like the eyes with lids but still our brain at night can mute or dull their inputs? JMHO.
Fish do not sleep in the sense that we do with full unconsciousness. They just shut down extra brain activity, but they likely keep "swimmming" or doing that twitch thing to keep themselves suspended.
It's probably the equivalent to day dreaming for us... where your eyes are open and you know whats going on but your not really paying attention. However, if I bear were coming to attack you, you could still quickly react.
At night my clown goes into a corner and starts swimming in a little oscilating up and down fashion. Entirely different from daytime activity. He just stays in one spot horizontally and just undulates up and down vertically.
When I first got the thing I thought he was sick the first night.
My Chromis turn recluse for the night
Don't recall what my yellow tang or any other critters do.
I like the wrasses, they make a mucous sleeping bag and they are set for the night. I've seen my tang's stuck in a crevase for the night. My clown's do the same thing, just move up and down in the same spot all night. They want an anemone to sleep in.