I have a HTW in my 180reef with 4 tangs. Quite docile and has never touch any corals or such.
Mine is small-ish and is bullied by the tangs at feeding time but he gets his share. Eats everything I throw in.
They do get large and can knock thing over.
I have heard of others keeping this fish in reefs and I am not aware of any coral nipping problems although ANY fish, IMHO can suddenly take up this habit in a home reef aquarium.
I've had mine in my reef for about 2.5 years. I've never seen it bother anything: corals, snails or hermits. The tusk will chase my exquisite wrasse on occasion at feeding time.
I think small shrimp or crabs would be goners. The tusk co-existed with a fountain (similar to CB) shrimp for over 2 years; the shrimp recently disappeared (don't know if it was old age, it was over 4 years old, or if something, either the tusk or PITA hawk, got it).
I have kept one in a 180 for a few months. Very coral friendly. It is hit or miss on invert compatability though. Mine like shrimp and the occasional snail. My hermits have all survived though. It is a great fish for a semi-aggressive reef tank. By this I mean it could either harrass or eat small firefish and gobies as it grew larger.
