I skimmed the article so I may only be reiterating a point made there. BUT, it is my understanding that ich is generally always present in water and takes advantage of fish that have become stressed (weakened immune system). Therefore in a tank with an ich outbreak, it is important to look for potential stress factors to avoid future outbreaks. Something like this can be difficult if NH3/NO2 are 0 and NO3 is low. I have found that for fish such as SA cichlids (prob cause this is about all I got) adding things like driftwood and peat REALLY help and even small, difficult, ich spots go away w/o raising the temp above 80 and adding salt. Sometimes its not what is in the water that stresses fish, but what isn't in the water.