These go by a number of common names - they are members of the bream family, Nemipteridae. Your's is probably the smalltooth bream, Pentapodus canius (Sometimes people put them in the genus Scolopsis, but that is incorrect).
How long have you had it? I've only had three of these fish over the past 15 years, and none of them made it out of a six week quarantine....don't know if it was poor handling prior to my receiving them or what (none of the necropsies showed any disease process). Three is not a really good sample set, but it does get me thinking that perhaps they are not as hardy as they appear to be at first.
Randall reports that they reach 26cm, and pictures of adults show that they lose most of their coloration at a length of around 8cm. He reports these are open water planktivores, but will also take benthic inverts. I think they are "reef safe" like a fusliler would be: might eat small shrimp, and need lots of open swimming space.
Jay Hemdal