If you have ich in your reef tank, the best way to get rid of it is to do a fish-only treatment. This means removing all the fish from the tank and treating them in a separate aquarium with an ich medication. Once the fish are cured, you can put them back in the reef tank.
To prevent ich from coming back, it's important to keep your reef tank clean and free of debris. Make sure to do regular water changes and monitor the water quality closely.