James and ATM-
lionfish and all scorpionfish will eat anything that fits into their mouths. I would guess that any small clownfish and certainly firefish are on the menu.
Next dwarf lionfish are reef-safe in the pure sense of the word meaning they have NO interest in corals. However -I call them reef-limiting, in that they will prevent you from having any moving invert, or smaller fish
Please read that lionfish article from the link I provided above, it goes into detail about the Q? you asked