Yeah, copper sulfate(chelated) and hyposalinity are the best known methods so far. But, if there is any parasite present in a tank, its inhabitants get infected with it no matter what...it's not a chance event....they just don't have any choice. (unless there is a way to intercept parasites before they get your fishes) Every fishes kept in the hobby have some kind of parasites with them in spite of your effort to sterilize them. It's all about maintaining an equilibrium. The weakening of the immune system is one of the biggest factors that are responsible for the outbreak of the disease and you know..... stress does such an effective job at disrupting this equilibrium. Even if you have almost perfect water parameters, but with stress still present, fishes are very prone to being symptomatic. So it's really important to have a near stress-free environment besides good water quality and proper diet.