I have heard from many people that they mind their manners, but like most things, it depends on the fish. You are always going to hear stories of butterfly fish that never touched a coral, or dwarf angels that ate every coral in the tank. One thing that I have learned is that there are no absolutes, that any fish is capable of doing almost anything. Its all an odds game, odds are in your favor with a crosshatch or bluejaw trigger that it will be behaved. But there are also decent odds that you are going to get one that will try to eat your smaller fish. ESPECIALLY if it is a larger fish. In that case a 7" crosshatch is used to eating fish the size of young chromises in the wild. It sees your school as a buffet of little tidbits that have nowhere to run when compared to the open water areas he WAS hunting.