I have noticed that sliding off topic is a natural part of the progression of many threads, just like my own comment thus farOf course there was not an answer to the OP question -
For those that don’t QT, why not
I received a Koi in the mail that had an open wound on one side. The fish were for a friend’s pond so I set up a giant tank added foam filters and made a holding pond to qt/ heal the little fish. I looked on here and found some recommendations for a general cure and after the fish were settled in I netted them from there pond and did a 10 gallon soak for 30 minutes and put them back into the qt pond. I repeated the treatment and kept the patient alive (after I was told that it would likely die. I don’t normally buy fish online so usually I don’t bring home fishes with open wounds.
I did buy a harlequin tusk in a hurry that had a wound but I dumped him in the reef and fed the tank fresh chopped live foods and a week later without meds he was healing and I still have the fish a few years now. I don’t qt because I try to keep the tanks running clean and feed well and injured or spotty fishes generally respond well and live.
The koi tank was an instant set up because I can’t give a buddy a sick fish. I still have them months later but when the water warms up I will give them to him with a long qt to insure that I don’t create an issue with his other ones.
I don’t qt because I don’t need to.