Steve, that's the point Brad and I were trying to make. The ich is always there, healthy fish don't succumb to it though. Stress your fish and the parasite will grow quickly. You can take a sterile tank and put a fish in there and the fish will develop Ich if it's stressed that means the fish carry the ich. So yes, your fish never get rid of it, yes it can die off in a tank but as soon as another fish goes into that tank it brings ich in with it. So, when I said it's present in most if not all tanks I mean tanks with fish. That being said, once a parasite dies it may leave behind an egg/cyst that can be dormant until a new host picks it up. I'm not sure how long that cyst can lay dormant with Ich.
Just a final thought, yes you can bleach, copper treat, bake your tank in an oven etc to get rid of ich out of a tank with no fish but as soon as you add a fish, you've got Ich in that tank.
Doug
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