Heat alone doesn't kill some strains of ich. I suggest doing a large water change(50%), then add salt. 1 tablespoon per 5 gallons. I usually add 2 tablespoons per 5 gallons but thats me. Increase the temperature to 90 degrees. Be sure to add a powerhead or bubbler because warm water holds less oxygen. Do 20% water changes daily for a week, replace the salt that gets removed from the water change. Ich usually clears up for me in 3-4 days when I do this.