for any treatment of most diseases if theres a cure, it will be on a thousand webpages, and i guess its good guppy posted this up cause theres lots of people asking about ich especially.
also it is though fish can become imune to it, and im pretty sure my 2 gouramis are, they are the only fish that have survived a couple of outbreaks that killed all other fish.
also prevention is a key, good water quality keeps the fish immune system up, and be careful when adding new things to tank- feeders, new fish, food, plants etc.