Your uninformed and what I might assume to be snide remark is just that.
In the ocean, the fish swims away from the parasite. Up to 30% of the population of fishes have the disease, in certain areas that have been studied. They are NOT cured nor become parasite free by eating or being healthy, they simply get away from more infecting parasites. At different times of the year, that population of infected fishes comes and goes. Tagged infected fishes are later caught miles away, found both uninfected and sometimes infected -- healthy and eating.
Few fish in the wild die from this disease. It's a poor parasite that kills its host. In the wild, the fish sometimes looses its infection by getting away from the parasites it helps reproduce, or the tidal/sea currents carry them away.
In the aquarium, that doesn't work. Our aquariums are not a bit of the ocean and when held in a captive environment, fishes become a buffet for parasites.
Your experience is anecdotal. If you can't see the above and have not done research, you are as I began, uniformed. You want us to take your word for it. But when you AND OTHERS have scientifically identified the parasite, used the product you think is good, then scientifically search the fish for the parasite, can it be told the product worked or didn't work. So far, none on the market have passed this simple test, but you want us to believe in your tank the product works. I have taken fishes just like you claim to be 'immune' or 'parasite free' and find them, under a microscope, to be infected. I have tried to boost their immune response (also by injection) and overfed super quality foods, to no success. When their skin is craped, their tail fin clipped and their gill clipped, the parasite is still there.
The parasite keeps on draining energy from the fish, no matter how much or well the fishes are fed or cared for, in the captive environment.
I won't continue this topic with you, but it should be known to those who are new in the hobby that there is no scientific evidence that even comes close to your 'experience.' And I will post my posts in those threads, in this Forum, where such misinformation is posted. Contact a professional ornamental marine fish veterinarian for further information, read appropriate journals, or go to extended educational college classes for the facts, if you can't get into what I have presented from my research.