Mine sleep. Where is depending on the pair. Some like their nems, some like my overflow pipe, some like torch coral, and when new, they just liked a corner in top of tank. They are fun fish. Mean, but fun.
Someone mentioned blue spotted puffer sleeping, mine does too in the corner on the left side of the tank about 5" from top. Find him every night as lights go out. Same spot. Funny fish. Also, my wrasses would always go to bed (in the sand) same time each night.
Cute ocellaris!
To the other person, not sure three in the tank is a good idea. Someone is going down for the count and maybe two with a maroon in there. How large a tank?