Not sure what your feeding, but when I mix up a batch of beefheart for my discus, the garlic gets mixed right in along with a bunch of nutritional supplements (Calcium +D, Amino Acids, Antioxidants, a general vitamin supplement, minced shrimp) Its really only a preventative, that doesn't always work. If you do get a fish with intestinal parasites, you will have to treat it with a medication.