This gets kicked around a lot, moreso of late or so it seems. There are those who swear by the healing powers of garlic and say it can "cure" ich. Others, myself included, won't go so far as to say garlic is a cure, but rather serves as an immune booster which can help a fish fend off a case of the illness. In a lightly stocked, low stress environment, an otherwise healthy fish would have a fair shot at keeping the parasite at bay, with the use of garlic. I use it as a regular food soak a few times a week. I recently had a small purple tang that contracted a mild case of ich shortly after purchase. It was in quarantine at the time (a very good practice with any new fish, btw) and I treated it with hyposalinity. After introduction to the display tank, he got a regular diet with garlic additives and has not been sick since. Keep in mind that he was one of three fish in the tank, the other two being quite small. Personally, i would not rely on garlic to cure ich, although as stated, some folks say it does just that. Two proven methods of treating ich are hyposalinity and the use of copper-based medications, the former being the safest. I sometimes think those that only want to use garlic are not willing to expend the effort to properly quarantine and treat with proven methods, but that is only my opinion. On the other hand, garlic has a great reputation for repelling all sorts of things! We use it in our dog's food in the hot months and he is never bothered by flies. Our horses receive garlic supplements for the same reasons, and we even take garlic tablets prior to and during our camping/backpacking trips to fend off flies/ mosquitos, and other nasties. It does work in these instances so I'm not pooh-poohing it's benefits. I just won't go so far as to say it will cure ich.