Why not letting them back? Perhaps other doctor may learn a thing or two about the disease/virus. It's better than just let them die off in some 3rd world country, and as a result, there's no cure for it. Imagine if everyone looks at the picture of J. Wade and the African tiger fish, and thinks, "OMG, that fish would wipe out my entire tank, and perhaps, ate my arm the next time I feed it." This hobby might end up with just fancy guppy and goldfish with that kind of thinking... There's pioneer, and there's whiner. Some born to lead, and some born to bee-otch!