I didn't have much luck with chemicals in curing ich. Could be that my fish picked up a resistant strain.
On AB Forum we discussed ways to cure ich using filters and salt. Salt (NaCl) at 2 tsp/gal seems to reliably kill the infectious ich swarmers. The only downside is that that concentration (about 0.3%) will kill plants.
Here's the link: http://http://www.aquaticplantcentra...ating-ich.html
I cured Ich without chemicals by moving fish from a new, clean quarantine tank equipped with a chloroxed Quick Filter every day for 6 days. By the time the Ich cysts dropped off the fish and released their infectious swarmers, the fish were safely in a new tank. It worked beautifully, but it was lots and lots of work!
After learning from my fellow ABers how reliably salt works, here's what I'd do instead. Transfer your fish to a hospital tank set at 83F containing 2 tsp salt/gal. Watch to see whether the spots decrease. At 83F, the cysts (white spots) drop off the fish in 4-5 days as part of the Ich parasite's normal cycle. If spots come off and no new ones appear, you'll know that the salt is working (killing the swarmers and preventing re-infection of the fish). If the salt works, your fish should be cleaned up in 5-6 days at 83F.
After the fish appear clean, wait 1-2 more days. You want to make sure that ALL the cysts have dropped off. Remember, there may be one or two left in the gills that you can't see, so be patient. (Each cyst can release 300-1,000 swarmers, so you need to make sure that they're all gone from the fish).
Meanwhile, keep the temperature high (~83-85F) in your main tank while you're treating the fish. At this temperature and without a fish host, the swarmers will die within 3-4 days. Thus, you should be able to safely return your fish to the main tank within 6 days of there being no fish in the tank. I waited 7 days and my fish were fine.