I want to point out bangaii are suppose to be one of the most hardy fish for new fish tanks. However, I think this is no longer true as many of these fish was harvested with many different wrong ways. The wild caught one can easily die to stress due to all the rough handling and regardless what you do, they just refuse to eat. I usually go with more costly tank breed one.
Did your LFS
tell you if it is wild caught or tank breed? What size is the bangaii?