man.. what a mess... I read not to mix copper and hypo because it's more difficult to monitort the copper and it can cause fluctuations in other parameters. I won't pretend to know anything more about it than that.
In my opinion, ich is going to exist in the average reef tank. Meaning the person that likes to pick up a coral or a fish, or a snail every so often. And doesn't thoroughly QT everything. Very few people I know QT every snail. And even fewer every coral. And the one point in which everyone thinks they do QT, and most don't effectively QT is that they QT multiple animals, from multiple sources (not just suppliers/LFS's, but collecters, and areas of the world) together. Or even more foolish... they may QT one animal for a month, then add another, and for weeks later add the initial animal to the display. Geeze. Nowhere is this more rampant than here on RC with all these elaborate builds.
That said. I built my 180 and ran for 2 months fallow with LR out of another reefers tank (that I'd known for about 2 years.) I then bought a group of fish from another reefer that had been in his 125 for 2-3 years together. He hadn't added any other fish in 2 years. They were all healthy when I got them from him. Out of the group, a 6 inch regal tang came down with what I thought was ich. In over 10 years of reef keeping I had never had a sick fish. I tried what many of you are suggesting, feeding, ride it out... etc. Well, it got to the point where the fish was suffering, and I didn't have the means to QT a 6" tang. So I found another reefer that did, and offered to give her the fish. I tore my tank down (180) to get this fish out, and still stressed him out to the point where he died in the 5 gallon bucket on the 1.5 hour drive to her house

None of the others have exhibited signs of any disease since September 2009.
I have only added 3 other fish since that group, and that was in Dec. They came, again, from a reefer I knew, with a healthy tank. I didn't QT them and added them to my display. 5 months later, no issues. I'm keeping my fingers crossed!!!
I have one fish in a pseudo QT right now. It is in a 12 gallon nano, that was a fully functioning reef for nearly 2 years. I remove most corals. This fish is delicate (CBB) and is being trained to eat prepared foods. I left the LR and sand in the tank, along with a few zoas and polyps. The fish has been in QT 3 weeks now, and will likely stay there for another 2-3 months. Why? I wanted the benefit of the biological filtration of the LR and LS. Given that the fish is undergoing food training, I needed a robust system that is stable as much food is being added. Also, I can do fairly large frequent water changes without shocking the system. I wanted to provide a lower stress environment than a stark QT tank. I think fish can discern plastic rocks from real rocks LOL The tank is small enough that I can catch the fish easily if it needs to be medicated. I can observe proclivity to eat polyps easily.
All this, and I'm obviously in this subforum for a reason right LOL
The tail of my copperband looks a bit odd to me. It's not ich, but I can't identify it as anything else. Kind of like a mother of pearl look on his white. For all I know, it's normal. Anyway, just thought I'd share my opinion of QT. Faced with my regal's case of ich again, I think I'll let him fight it out in the tank. Not stress the sick fish and all others by attempting to catch him. But I do QT all incoming animals for which I don't know their history.