Use the UV!!! I wouldn't treat the tank, if the fish are valuable enough, pull them out and treat them in a hospital tank. Keep in mind that it takes about 30 days at 75 degrees for a tank to remain fallow to guarantee elimination of all ich spores.
What size is the tank? That heater ideal for about a 30 gallon. What type of fish are in there?
Nothing good happens fast in an ecosystem.