[TheOldSalt]

Larry is right about that. Tropical fish diseases picked up in an aquarium can wreak tremendous havoc if infected fish are released into areas where those diseases don't naturally occur. You would have to keep your killies in a separate room from all your other tanks and make absolutely certain that they were never in contact with anything which had been in contact with your other fishtanks if you plan to release them later, and even then it's likely illegal to release them anyway. That's one of the greatest responsibilities you have as a fishkeeper, protecting the natural environment from your hobby.