i hope you QT your new fish in the future to prevent this from happening again.
ich has to go through its "cycle" to die off. if it is attached to a host (fish) it cannot be killed. it can only be killed in its free swimming stage. salt is a good way to fight ich, but as batman said, most fish wont like it.
It has been found that Ich does not infect new fish at 29.4°C/85°F (Johnson, 1976), stops reproducing at 30°C/86°F (Dr. Nick St. Erne, DVM, pers. comm.), and dies at 32°C/89.5°F (Meyer, 1984), 
So the first step would be to increase the temperature slowly, 1°C/2°F per hour until the correct temperature is reached. This temperature should be maintained for 10 days, and then slowly returned to normal.
25% daily partial water changes will provide several benefits: It will keep the water very clean, which will help fish cope with the stress of the disease.
Use salt. In a non-planted aquarium with tolerant fish, the addition of Aquarium salt at the rate of 1 teaspoon per 4 liters/1 gallon of water disrupts the fluid regulation of Ich. Do not add salt crystals directly to tank. Always dissolve salt in a small amount of tank water before adding to tank. This dosage may be repeated every 12 hours for a total of three treatments. When Ich is gone, salt is removed with daily 25% water changes.
's were taken from an article ive found on aquahobby.com)