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Well established fish populations (I mean years- and most people responding in agreement here are VERY experienced with long-standing stable systems), do seem to be able to avoid outbreaks even when new specimens are introduced with minor infections. I have noticed that unless there is stress in the system ( poor water quality, temp swings, poor nutrition, over aggression etc.) existing populations rarely develop symptoms, and if they do, they are minor and disappear quite readily on their own. Stress IMO is the key factor.
As a rather depressing personal example, I recently added a wonderful C.ulietensis Butterfly to my 10+ year old reef to help with a long-standing and out of control Aiptasia problem. The fish arrived in good shape, but had a few spots. Normally, I don't worry about this as the fish population has proven bullet proof over the years under these circumstances. As expected, the old fish remained unaffected and the new Butterfly was recovering nicely. Then, I made the mistake of breaking down the system for a much needed all in 1 day redesign. It needed to be done and the corals are much better off for it, BUT all the fish within 48hrs. came down with a seriously bad case of parasites and I lost most of them, some 13+ years in my care.
The point is, it was the stress and destabilization of the system that caused the problem. If I had left the system alone for another month or so, I am quite sure this would not have occurred.
What I currently find more useful than full blown QT is the use of an in-tank acclimation box, that allows new specimens to get used to their new surroundings and water quality, enables you to ensure they get food and are feeding well without competition, and helps ward off potential aggression from established tank mates by allowing them to get used to the newcomer without being able to physically get to them. This strategy also enables you to easily remove a new fish if the need for whatever reason arises. |