..is a red herring and I don't think is really very apart from the QT procedure.
May as well be called chaos management. ;)
Lucky for us, the immune system (in total) has been design for no less purpose than this one.
I'm not sure what we hope to accomplish
without it by ignoring it.
In the end, I think we will collecively learn not only that we have been subverting our fishes' immune system (most of the issues have been put on the table more than once) but how, why and when.
Some of this is already clear....anything that can be considered a controllable stress should be controlled.
E.g. Population density. Feeding. (Maybe being a beginner ought to be on this list of controllable stresses as well!)
That's at least two things eminently within our control and which go directly to immunity support/suppression.
If you don't think you can implement every aspect of Paul's system because you don't live as close to the sea, for example...
Then support immunity instead by lowering stress – keep a lower stocking density than he does. (Just an example. One option of many.)
I see no reason to expect lesser results than Paul gets if you can lower stress for your fish with a serious mind and feed them as well as possible. For feed, I would consider quality probiotic food a very acceptable minimum. But folks should give more consideration to live food. Most locales have insects and larvae that can be found and/or cultivated.
Earthworms are common in most places. It doesn't have to be clams and blackworms if those are impossible for some reason.