What kind of system is the fish in? Reef, fish only?
If it's starting to rough itself up, you're likely going to need to treat with antibiotics...which cannot be done in a reef and shouldn't be done with rock and or sand due to absorption. Ideally, I'd setup a qt appropriate for the size of the fish. You can buy a bottle of biospira and soak a sponge and a bag of biomax in it(with fresh saltwater to completely submerge) for a few hours/overnight and put them in an hob filter. That'll quick cycle the qt. Depending on which ich treatment you're using, you can also mix the antibiotics with copper if it starts looking bad. Just keep some airstones or, preferably, a powerhead pointed to the surface to help against bacterial blooms
