SURE FIRE MARINE ICH CURE!
I have found the ultimate cure for ich! Empty the tank, get rid of the fish, dry out and sun bleach the rock, sand and equipment. Poof! The ich is gone! (One alternative method involves nuclear weapons but, they are getting hard to come by now that Sadaam is out of business)

Now, seriously, ich seems to be an ever present problem. There is no cure except to break the cycle by removing the host and leaving the tank without fish long enough for the parasite to die off- weeks to months. New fish may still carry the parasite but be resistant and only fall victim to it under times of stress.