As a direct way to kill off th ick you are rght. but the garlic Is believed to raise the ammune system of the fish there for helping the fish to fight the ick off. cant be proven if the galic is the actual reason your fish got rid of ick but im sure it helps in some small way.
As for UV
lights. it sterilizes the water that passes through it anywhere from algae to parasites. So if you look up the life cycle of Ick there is one stage of its life where it is free floating through the water where it bumps into the fish making it the host. but if it runs through the UV
light before coming into contact with the fish then it dies off, But if th ick comes into contact with the fish then the UV
ligt will have no affect on that.
I dont belive a UV
light will be a cure all but in my opinion if you can stop one stage of the icks life cycle then you will ultimalty win the war so to speak.