Ich is a parasite that fish can get. Raising the temperature and adding salt will treat, or anti-parasite medicine.
As long as the Ich parasite is protected inside its cyst, it is virtually impossible to get to - the levels of medication that would be necessary to affect the parasite inside the cyst would kill the fish as well. This is why we must focus on the free-swimming tomite stage when the parasite is much more vulnerable.
Bring up the water temperature to 85-88 degrees F (if you think you fish can handle it).
As mentioned above, Ich can attach itself to the gills of fish and make it hard for them to breathe. It is therefore a good idea to increase aeration in the aquarium to keep the levels of oxygen really high. Adding more aeration is especially important if you increase the water temperature since cool water holds more oxygen than warmer water.
Add roughly one teaspoon of salt per gallon of water. (You can adjust this amount depending on how salt tolerant you fish are.)
Carry out a series of water changes and clean all the gravel. Changing around 50% of the water once a day is recommended.
Continue the treatment for at least one week, since you can only kill the free-swimming Ich parasites. The speed of the life cycle is temperature dependant (it will for instance take three days at 80 degrees F) and continuing treatment for an entire week is recommended to be on the safe side.
If this is not enough to combat the Ich outbreak, you need to visit your local fish store and pick up some anti-Ich medication. Unfortunately, the Ich parasites seem to become more and more resilient towards treatment each year. Lazy aquarists and pet shop keepers are often tempted to constantly use medications to fend off disease, instead of devoting themselves to frequent water changes etcetera, and this makes it easy for resistant strains of parasites and bacteria to develop.
Soil Substrates Guide:
Part 1--------- Part 2