Ich is the devil, and it will continue to get worse. You really only have two choices for treatment that have been proven effective. You can A.) set up a QT tank, move all of your fish into it and use copper based medication to treat your fish. You need to leave your other tank void of fish for at least 4 weeks, but I'd go 5 just to make sure. This allows the full life cycle of ich to run it's course, and then die without a fish host.
The other option, and the one i prefer, is to do hyposalinity. Once again, you set up another tank and move all of your fish into it. You gradually drop the specific gravity down to 1.009 over a 3 or 4 day period. You leave your fish in there for 4-6 weeks, and then gradually raise the specific gravity back up to normal levels. This keeps the ich from reproducing, and thus they all die off.
No matter what route you choose, it's gonna take a while. There is no other way to get rid of ich for good though. UV kills good things along with bad, and it never will completely get rid of ich. Garlic, though it is good for the fish, doesn't kill ich either. And even though your fish may look healthy and have no ich visible to your eyes, they will still probably have it in their gills. You gotta destroy it, and then never put anything in your tank ever again without first putting it through QT.
To get good, detailed instruction on how to treat it, go to advancedaquarist.com, click on archives, click on aquarium fish, and then read the 5 articles on
"news from the warfront with cryptocaryon irritans" They are excellent articles that cover the life of ich, and how to treat it.
Hope this helps.