I think you should give all fish a good long quarantine before you put them in your pond, especially if they come from a place like Walmart. If the fish die, well, they were dirt cheap. If the fish turn out to be healthy, they're just fish. If you like them it doesn't matter whether or not they'd be taken seriously at a fish show. But if it turns out Walmart has been raising a persistent parasite along with their fish, and you don't quarantine, then you've got a problem.