One Word:
Garlic!
I add garlic extreme (kent I think) to my frozen food and soak my dried algae (Julian's sea veggies). It works. I usually add garlic every other week as a precautionary method or more when I see a spot. I also keep cleaner shrimp and cleaner wrasse (not red sea!!!)
As my friends can attest, I love my tangs.
I'm able to keep Achilles, powder blue, purple, hippo, yellow and sailfin without UV or meds.
Keep the stress levels down, water chemistry constant (I have had constantly bad water in the past with no ich) and they should get over the visible infection on their own.
That's my .02