Yep, that's what they do, particularly when new. He watches. Late in the evening, when he feels confident, he'll come out and tootle up and down the glass. He grabs mouthfuls of sand and sifts it through his gills. If you put something into your tank he's scared of he may not come out for months. Many people have had them disappear for 3 months on end: he's scared of purple tangs, in particular.
They're not fond of other things that are yellow. They hate others of their kind, or that look too much like them. They bluster more than they bite, and usually become accustomed to the intrusion of another small fish that just regularly goes through his territory.
They're one of my favorites---bright, very much visible if you don't have threatening fish, and funny in his behaviors.
He'll like a couple of Formula One Sinking Pellets dropped near him. He'll probably dash out and get one and take it back to safety to eat.