UV may or may not help remove ich. I wouldn't go that route unless you already had something. garlic soaked food and a healthy tank (good params) are your best bet. you could yank the fish and treat him, but unless you are experienced in that method... I would not bother trying. odds are pretty high you will shock the fish's system in some way that ends up with a dead fish.
Pick up some rods food, nurtramar prawn ova eggs, and algae/nori and offer a varied diet to make sure he is getting everything he needs to fight it off. add a cleaner if you can, but that will not remove the ich, but it may help lessen it which would allow your tang to become stronger and fight off the rest him/herself.
But like said above, you will need to feed algae regularly (I feed daily, that may or may not work for your fish/system) to keep a health tang.