| Lookin' for a fish that cruises the tank,won't nip corals,and fit well in a 53g....well,my first thought was a Longnose Hawkfish.No swim bladder,but they like to perch out in the open.Some consider it a jumper too.
I'd suggest a reef-safe Lamarck's Angelfish,but like most Angels, they're cute when small,then become the bully of the tank.
Guess a Copperband would fit the criteria ,if you can find a one that likes to eat.
__________________ Larry  The solution to pollution is dilution. | 
