Brown powder Tang purchase

Local fish store has a 3in brown powder Tang, it's beautiful. I've gone in there twice with the intentions of buying it and the salesmen proceeded to talk me out of it. They say that the powder Brown Tang is prone to getting sick. I would like to ask people on this forum that have actual experience with a powder Brown Tang how it went with you. I do not understand why a store would stock a fish and then not really want to sell it. Somebody has to have had success.