Long nose hawk fish. He's a little tank. He's so cool the way he hangs out on the rock, just standing there waiting for me to feed him again - he's such a beggar!
Go peacefull and get a couple of fire fish, more than 5 and they should school. No sure what your limit is for a 55. Or how about a Catalina Goby, there small & V beutifull, and probably about the hardest thing for its size on the reef, one of those would probably be able to see off a small grouper. Bangii Cardinals are cool too coz you might even get them to breed. And in a small reef you have a good chance of raising the fry.
i have a sargassam trigger, in my 55, along with 2 blue green chromis. the sargassam thinks hes a chromis, they never leave each others sides.he has been an exciting fish to raise, and he has never defiled anything. except for the occasional snail toss.