That's what I thought. So it's a juv. Coris gamaird that you have and not a yellow coris. If so, you definitely were sold a bill of goods. This is not a reef safe fish. As they mature, they will play havoc with your decor and some of your smaller reef safe fish. ( But I think you will agree, they are GORGEOUS as adults
I'd bring him back to the LFS
and find a better LFS
to go to. Tell the owner why you will not be stopping in anymore as well. Owners need to know when their staff is the problem with customers.