I drained my 400 gallon, fully stocked FOWLR tank 1 week ago because of an ich outbreak. I have a 240 gallon HT running. I have several large fish- a 9" Emporer Angel, 8" Scribbled Angel, 7" Personifer Angel, 7" golden puffer, 5" clown trigger, 5" humu trigger, pair of bird-beaked wrasse, pair of maroon clowns, plus multiple smaller fish. This experience has been a real inconvenience for me. I learnt the importance of quarantining new arrivals!
UV might help prevent an ich outbreak but will not treat it after it has occured (I have 2 80W high output Emporer Aquatics UV sterilizers running on my DT). Cleaner shrimp/cleaner gobies won't cure ich- I tried that. Neither will soaking your food in Garlic and Selcon. The worst thing you can do is waste your money on any of those "reef-safe" ich treatments (I never did that- you can read all over Reefcentral forums that those don't work).
My advice- bite the bullet and fallow your tank for 8 weeks.