He should be fine for now, but I would bring him back to the retailer. He really should be in a larger coldwater tank. But what a fun experience to get an "unknown" fish. It doesn't sound like they are kept very commonly. A year ago, to keep my comet goldfish company, I was looking for an American species of minnow--a red horse--but couldn't find any. Then I realized I would need a much bigger tank anyway so stopped looking. These sites say they are omnivores, so he should take whatever you feed him when he gets hungry enough. If he was wild caught, he may just sulk for a very long time.
