Ive kept two long term now(1+yr each), and although they have been model citizens towards my corals their have been isolated incidences. Last year I was getting a mysterious decline in some of my Leptastrea colonies. One colony in particular was having some polyp bail out sessions. This is when my CBB took a bite of the sloughing tissue, and it was on! He quickly made it one of his "stops" in his routine tank patrol. Like a nasty habbit, he chisled the coral past the quick. Once I removed it and let it heal in another tank for a couple months I put it back and everything was fine. He did this with two morphs I had of Leptastrea as they were conveniently suffering around the same time. After that he's back to being a good boy again, and everyone's getting along just fine.
There's several things that I can attribute there successfull keep/survival. Size and health, it should be bigger than 2"( I speculate this to be true because younger specimens havnt had an opportunity to develope a diverse full spectrum of there normal diet, therefore there will only be a small variety of foods that it would accept, and more than likely live foods only), beside a suitable size, make sure theres no signs of scratches, ich, or any sporatic behaviour including whipping or "flashing", as this may be a sign of flukes or other ill parasites. Secondly this beautifull fish grazes ALL day on worms, featherdusters, pods, and aiptasia(the second reason why I wanted this fish) and other live critters so a well established tank is a must IMO. Along with a healthy population of pods and such the only food Ive witnessed all of mine actually eat is mysid shrimp. They LOVE IT! Now they'll strike at other foods, like brine, arctic pods and such, but mine NEVER eat it. My first one even was tempermental bout mysid at first, but tricked him on a moonlit night in my tank and put the mysid feeding in front of a powerhead, with the low light and movement apparently he thought it to be live and immediately started striking and devouring the lil shrimps.
Here's an old but favorite pic of the lil guy, he's almost 2 years old now
-Justin