Ich is only killed when unvisible and free in the water. The visible spots on the fish will not be killed with any treatment. This is why it is important to heat your tank for 24hrs to kill off all ich in the water and then lower the temp again until you see the spots disappearing off your fish(this is part of the life cycle of ich). This means the ich has left your fish and is now free in the water. So reheat your tank to kill it again. Repeat this process until no ich is seen for a week.