Tank mate(s?) for a Maroon clown in a 40g tank?

[DanG]

Yes, the clown is a lazy lazy fish. He usually won't stray much past a foot or so away from his GBTA.
Originally he was in with another maroon, but she proved way too agressive, so I returned her and for the last 2 months it's been just him.
I'm somewhat concerned about an angel as I don't want to rule out coral. There's the GBTA, a rock with some zoos and a rock with some green star polyps, but I was thinking of getting a head of frogspawn, some candy cane or maybe an open brain coral.