I'm one of those that prefers to use
Hypo salinity in a QT environment
Yes, catching fish sucks, but there are many methods that work;
You can try trapping, netting at night while they are sleeping, and lowering your water level, to name a few
You asked for suggestions;
1 - remove all fish from tank and QT in Hypo, all the while your DT is kept fish-less for 9 weeks to starve the MI
2 - DT is fish-less as in suggestion 1, but treat your fish in QT with a more drastic approach, using copper-based medications in the QT, but there are long-tem effects on fish health associated with copper, and it's hard to monitor the correct levels
3 - use garlic, herbtana, or other stuff in your DT and see what happens
Many peeps have had success with with option 3
I haven't had to deal with it yet in my DT, so I can't give you personal experience, but I don't believe in it either ...
Fish health and immunity in dealing with MI, and concentrations in your DT, has some part in dealing with MI, so again, I won't rule out option 3, but it's not my choice
Concentrations of subsequent generations of MI can become very large in a glass box very fast ...
Eg: - in my 20g QT, a Royal Gramma had a couple spots on day 2, many spots on day 3, no spots on day 4, and then was totally covered on day 7 !!!
I QT all my new fishies, and have had MI in my QT ( the Gramma ), so I always keep them in QT for observation for at least 6 weeks
OK, ya, I only held my Foxface for 3 weeks in the QT, but knock-on-wood all was good with him
My tank appears to be MI free, so I am loving my QT ...
Good luck with whatever you try