There seems to be alot of information out there about the Ich parasite. I am not a marine biologist but I have dealt with it a few times.
Check out this link.
http://www.petsforum.com/personal/tr...osalinity.html
I have found this information quite usefull.
I tried quarentining all my fish and that worked well completely removing the parasite. However, I did have losses due to the stress of catching all the fish and putting them in a smaller tank. If the fish are eating, I would just wait. As the article states, Ich will go away on it's own after 11 months or so assuming that no more parasites are added to the tank.
Just my 2 cents but I'd leave them and not add anything else for the 11 months. You already said that you had all the fish on your list. After that time, carfully add fish after quarentining them to be sure you don't reintroduce the parasite.
If you have any questions, send me PM.
Thanks.
Garrick.