Nothing has been scientifically shown to eliminate ich other than copper or hypo-salinity. I think the majority of aquarium keepers opt for the 'containment' approach rather than eradication.
If you want to eradicate ich you'll have to quarantine them and either use copper or follow a hypo-salinity treatment.
Many people believe garlic has helped get their ich issue under control. Fish are naturally resistant to ich. They have a 'slime coat' that, with healthy fish, is usually sufficient to protect it from serious problems from the parasite. Garlic may contribute to the fishes ability to produce that coating. Or it may provide other benefits. Or none. Who knows.
Many of the commonly available commercial remedies involve a pepper component which supposedly improves the fishes ability to produce the coat or otherwise enhances the coat's ability to withstand attack from the parasite.
UV, when used properly, will kill pretty much anything that passes under the bulb...and therefore it may help reduce the overall numbers of the parasite in a tank but it is also not a cure.
What you'll find is that all the evidence supporting any other method of treatment than copper or hypo-salinity is anecdotal, not scientific. You'll find plenty of people that believe in garlic or a commercial product or who knows what else -- as well as plenty of people that say all of these 'solutions' are junk. The truth is nobody knows either way. But lots of people like to feed garlic for one reason or another.
FYI, buy pure garlic extract from a supermarket and save yourself a boatload of money. There is nothing in the stuff marketed in the aquarium industry that makes it special/better.