You just started world war III. However, I agree, Ich is a parasite it is transmissible, and will lay eggs that live in the rock / sand for multiple weeks waiting for a host to arrive. However, I do not QT fish. I manage fish. There is some truth to stress breads illness. If fish are in a healthy state they have thicker slime coats that prevent parasitic infections. Not saying it can't happen, but reduces changes. Feeding nutritious food, adequate amounts of veggies, and low aggression environments promotes this thicker slime coat on the fish. When stressed, the slime coat thins and parasites take advantage of the weekness. Even then, the ich can leave the fish and the fish can fully recover if kept healthy during the infection. I'm 90% sure I probably have ich in my tank, however, I have not seen any fish with any signs of it for a couple years now. I've seen fish missing scales because they're dumb and decide to run into my acros while chasing a piece of food...
There's one day I forgot to feed them their daily frozen food. The next day I saw that my blue chromis had some major damage to scales and was hanging out at the top of the tank and almost let me touch him a few times. I thought for sure he was a goner. I resumed normal feedings and fed heaver than usual. And 2-3 weeks later you wouldn't know anything had happened to him. I thought for sure he was gone. I thought about putting him out of his misery. But, nope, just needed food so other fish would stop picking on him. The chromis pretends to be one of my anthias. But they know better...
