Slowly adjust the temp to 86 degrees. I do 2 degrees every few hours. There are some articles on this site about the life cycle of ich which is a parasite. There are ich meds, the Kordon brand Herbal Ich doesn't work in the least. Malachite green can be used and something by Mardel called Quick Cure is supposed to be good. I have one tank with ich and I tried the heat treatment a few weeks ago and it came back. There are resistant strains I guess. Now I am trying this stuff at half strength because of a pleco in the tank. Actually I'm using a combo of this med and heat. If it were me I'd try heat first in its own. Some people add aquarium salt.
You may want to quarantine new fish for several weeks before adding them to your main tank.
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