I treated for 10 days using this stuff
http://polyplab.com/medic.html and I have never had ich in my tank since. I wished I had used it sooner. The gal at the fish store compared it to buying flea collars to get rid of fleas (which only kinda work) vs buying Advantage and ending the problem (because it doesn't just kill the flea, it breaks the reproduction cycle).
Good luck!