Most reputable LFS's will hold the fish in QT before selling it. The one I stick to does this. Also you can ask them to hold it for a week, make sure its healthy and eating well. If they won't then I'd think about shopping elsewhere. My store will not sell a fish that he wouldn't put in his own tank. I can only respect this because he has pointed out things wrong w/ them that I didn't notice. Could of just took my money like a couple of LFS's I know.