Tangs.....do they sleep???

[talon4x4]

When my moonlights kick on at night every fish instantly goes to their hiding spot (it amazes me how instantaneously they all disappear), except the powder blue tang. He always seems to be swimming around. And on the rare occasion he is hiding as soon as anyone goes near the tank, out he comes.

I can do a water change at night an he is the only one to come check it out.

Is this normal?!?

[betamed]

my tangs all sleep. powder blues are usually pretty high strung paranoid fish so maybe he has anxiety issues or night terrors or something.

[hng]

My regal blue wedges himself into the same crack every night and goes to sleep.