I put fish with ich in my tank all the time and don’t treat for it and it will go away with time, if the fish is healthy. None of my other fish get it or very rarely show one or two parasites. My powder blue was an ich magnet when I got him he was covered from nose to tail. He had it several times until he built up his slime coat, now he never gets it. I have had him two years now. Keep him fat feed him all the time, they eat constantly in the wild. You can kill him by setting up a small empty hospital tank with hokey filtration and moving the sick stressed fish that needs a large tank with good water quality out of a stable system with plenty of food and hiding places and messing with salinity. The fish should be fine and all the other fish as well. I never QT my fish and I have sold a lot of show sized beautiful tangs from my tanks that I have grown from small fish over the years. Ich is nothing to a healthy fish, it’s the sick dying fish that die form it as a secondary problem brought on by the sickness. Ich isn’t what kills the fish it’s what does them in. I have been doing this for years. There are other things that are more dangerous other then ich to worry about getting into your tank. You should QT if you have the space and money for a real system, not a ten or thirty gallon tank lol.
