I think you might be making his point. He’s saying that doing all of those things requires effort that (I’d wager) most people aren’t willing to do. I have ich in my larger display and I do nothing about it (6 tangs). However I’m strict about my ich-free smaller display (5 tangs) but I actually don’t put anything new in there. But if your tank is newer or you’re a fish collector of sorts, or you like adding new coral, or you like to replace your CUC, well that’s a lot of work to do a super strict QT of everything.I mean starting with dry rock and "live" sand theres no risk for ich. Then QT coral and inverts and your fish.
Where could ich be introduced?
My ich came from a PB tang I thought I QTed well (and I’ve been at this a while). It happens. As long as it’s not velvet I don’t worry about it.
In no way am I saying ich can’t be prevented or eradicated, but there are probably many tanks that have it and don’t know it.