Puffers + crabs = snack food.
I would also be wary with the blue devil damsel, they are quite beligerant. Otherwise, it will depend on which one you get, the green/purple or the white/purple. The green ones tend to be a little more reclusive and hide in crevaces/underhangs. The white ones usually stay out in the open more and prefer to inhabit LPS
type corals or anemones. They are by far more commensal than the green ones.
Both are primarily filter feeders but will scavange as well.