You shouldn't have to use medications to treat ick. Slowly bumping up your heater to 84* should do the trick. You need to do a gravel vacuum everyday to suck up any ick that fell off the fish, or else it can reinfect. I'm not sure how long you continued treatment after the ick has disappeared though. I'm thinking maybe a week?
And since you're not using any medication, I don't think you have to worry about doing any damage to your moss