According to Scott Michael's Reef Aquarium Book the Melichtys Niger aka Black Triggerfish is reefsafe with caution. He says that it is occasional threat to some stony corals, some soft corals, some ornamental crustations, and some other invertebrates.
I have had a Blue Chin triggerfish for a few years now. I like him but he is very clumsy. He will break pieces off of SPS corals while swimming around. I have never seen him nip at any corals but I have noticed that I have not seen my cleaner shrimp that I added after him for a long time. Like said in the previous post...keep them fed and they should be fine. One more thing....be ready for the spitting. They will spit at you during feeding.