Strange yellow tang behavior?

Ive had a yellow tang in my reef tank now for about 4 months. I have recently noticed that right after i turn the lights off at night he will patroll the tank and make sure all the other fish are hiding in the rocks. After hes chased them all into the rocks he will go in himself and check once or twice then i think goes to sleep himself. Do tangs usually police the other fish at night to make sure they are hiding and sleeping safely?

 

I'm not sure, buy my dwarf angel does the same thing. He swims around for awhile after lights out and gets mad if anybody ventures out of the rocks lol