I have read conflicting reports on the benefits of garlic, but one is for sure: Your fish will love it and eat (for the most part). The fact that they are eating well will help them fight off parasites and sickness, even if the garlic itself does not have a medicinal effect (which it might). I use Kent Extreme Garlic with one feeding each day. It has not seemed to have any effect on water quality parameters or my corals. I do not know of any side effects. If you search there are some really good threads on this topic. I remember one where Richard provided a lot of really good info regarding the use of garlic.