Well if you keep them quarantined for a couple weeks with no sign of ill health I would imagine the risk of passing on infections is reduced, but it does nothing for the potential parasites. You could either use some medication for parasites of freeze the feeders. The choice is up to you, I have never had a fish fall ill from the goldfish feeders I give them. For me at least, waiting for little guppies to breed and grow or convicts to grow is not feasible. That space I dedicate to breeding rodents. I just make my goldfish fat, freeze them, and feed them out. Or the market fish. I never was concerned too much about parasites,most of my predatory fish were probably wild caught anyway and always exposed to fish with the occasional worm in them.