As much as I like to say you will get rid of it, I cannot honestly do so. I emptied my tank due to marine velvet. I kept the fish out for 2 months, actually about 9 weeks. Kept only the inverts in the display tank along with coral. I put all my fish in a 45 gallon tub I got at walmart with a hangon filter with a couple live rocks. Used Cupramine and tested almost everyday with a salifert test kit. This was to make sure I was at the correct level as I wanted to make sure the velvet was gone. Long wait, along with weekly water changes got very annoying but I kept on for 9 weeks fishless, well kind of they were just in a different tank. Back in they went and sure enough the ich was back not long after. I didnt add anything new and am still very careful to this day(qt and dip). I became curious on why it was still in the tank and got to reading about it being dormant for a looooonnnngggg time. I dont remember the exact number but way longer than I could ever do. I want to say it was well over 6 months.

Anyways on a good note, I dont think I have ever lost a fish to ich. Once an outbreak occurs, always when I add a new fish, I make sure everyone gets alot of food. My purple tang looked horrible a few weeks back when I added a pyramid butterfly but is now spotless. I have just learned to live with it as I wont qt the whole tank again unless I have to.

Another thing you might want to consider is ich usually occurs when fish are stressed so is there anything you could do to limit the stress they are receiving?