[untamed]

I'm well down the same experiment. I'm leaving things alone and just watching my fish. My Achillies tang has always had ich to some minor degree. In spite of that, it has never visibly infected any other fish in the tank.

I've recently added a powder Blue Tang, who immediately got ich very bad. Again, I did nothing. His ich has now all but disappeared, but I expect it will return shortly.

I just have to believe that eventually, the fish will build up some sort of defence against this parasite. Meanwhile, it doesn't really seem to bother them that much.

I suppose it is an easy decision to make because the cure of removing the fish, treating them, and leaving the tank fallow for a time is worse than the disease at this point.