") is a parasite, not a viral infection. It is caused by the cilliate "Ichthyophthirius multifiliis
", an organism, pear-shaped to spherical in shape and .2 - 1 mm in size. (the macronucleus is horse shoe-shaped and the micronucleus is spherical). Ich spends most of its life on a host fish, feeding off the skin, digging sealed off hollows into the flesh. The parasite has a 3 stage life cycle: 1, growth, spent on the skin, 2, cyst, when it drops to the bottom of the tank protected by a gelatin covering and then dividing, and 3, the infectious stage, when pear-shaped zoospores seek a new host. The cyst can divide into as many as 1000 zoospores, which have 70 hrs to find a new host. Ich is highly contagious, and survivors can acquire an immunity, but many remain dangerous, since they may be carriers without showing signs of the disease. This is why medication is the #1 solution to resolving the issue.
Because of the temperature tolerance limit for the parasite, using aquarium/marine salt treatment of 1 tbsp/5 gallons and raising the temp to 84 degrees should safely rid your tank from the parasite. The salt will affect the parasite and will act as a muscle relaxant for the fish. The use of salt can also help to avoid/prevent the chances of secondary infection in the fish.
One thing to note: Not all fish can do well with salt in the water. If in doubt, please ask for help before putting it into the water. When used as a medicinal treatment, add the salt directly to the tank, slowly, and then stir slightly with your hand to circulate it. If you premix it into a small amount of water, the chemistry of the salt changes and you will lose the benefits of using it at all.
An experiment to try: Take a small cup, add a large amount of salt to the dry cup, then slowly add just a little bit of water, and hold the cup in your hand, with the bottom of the cup resting in your hand. If you hold it for a few minutes, you will notice the cup becomes warm, sometimes to the point of not being able to hold onto it. Now, take another cup, same kind of cup, or reuse the same cup after rinsing it thoroughly. Add water to the cup, and then slowly add salt. There should be no temperature change. The chemical reaction between the salt and water differs according to concentration and in which is put into the container first.
When medicating using salt, if the salt is added slowly, it will not burn the fish, considering it is a fish that does NOT have a low tolerance for any salt.