What about the fact that there is ich in both fresh water and salt water. For salt water, you lower salinity, for freshwater, you add salt. Could it be possible in a fish store that these two strains of ich could come together or could be placed in an environment where they adapted to different water conditions. How could something so similar exist in opposite conditions without having to somehow adapt to it. In the wild, what if a fish having ich swims up a freshwater creek, or the opposite? You see adaptation in viruses, parasites, and other things all the time, it is logical to think that the ich parasite is able to adapt if given the time.
I remember reading something that when dropping a saltwater fish in low salinity water, the change in pressure causes the ich to explode. If the lowering of salinity was done gradually, the parasite could adapt to survive the change. Just some ideas to think about.
