I worked at 3 ornamental fish farms, Area water gardens, Southwest Florida tropical, Old World Exotics, all of them only treated sick fish to prevent loss. Absolutely no preemptive treatment as a quarantine method.
Fine - Why? Sorry to me reading this doesnt make sense - except to prevent loss why else would you treat? I never suggested treating in a QT TANK - in fact as I've said at least 10 x - I dont QT fish before I drop them in my tank - so what does this have to do with me?