I've always treated ich with heat and huge water changes. I start with an 80 percent water change When you turn the heat up, add an airstone. Turn it up to 86 for 3 days, then down to 74-76 for a couple of days and then before you turn the heat back up do another huge water change to remove as much or the free swimming protozoa as you can and then up the temp to 86 for another 3 days, lower it back down to 74-76 for a couple days, water change, then increase the heat again. Do this for 2 weeks and your ich will be no more.
You see ich stop reproducing at a certain temp and then die a little higher, but you can still have dormant spores in the substrate. Lowering the temp allows it to resume the cycle again so you can kill it in the free swimming form, which is the only form susceptible to being killed.
Want to prevent illness? QT all new fish for two weeks.
