Clown Triggers are impressive fish. They could, in my opinion, be kept in a 100 gallon tank, or even a 90, since captive specimens over 9'' are rare and something to be proud of. A large specimen will also sell for mega bucks.
They are also impressive predators, and pose a significant danger not only to other fish and invertebrates, but to human divers. Their "cousin" the Titan Trigger in particular is a very dangerous fish. I would imagine adult Clowns have few predators, most of them huge Elasmobranchs such as the Tiger Shark.
Gymnothorax tesselata is also known to eat small ones.
Baby specimens are suitable for community aquaria, and adults can be suitable too as long as tankmates are tough enough to take a savage beating and also intelligent enough to get the hell out of the way.
Porcupine Puffers come to mind, as do Undulate Triggers. Clown Triggers usually turn mean once they hit about 8''.
On the bright side, these fishes are very intelligent, as all Tetraodonts. And as you probably realize, they are very colourful and personable, and in my opinion these outweigh it's bad points.
Corals are safe with these fish, as are some of the commonly kept "cleaner crew". Most other invertebrates will probably be mauled (or crunched).
They will accept most foods. Ideal are mysis, squid.
-Lynden