I think that's a misinterpretation. Most of what I've seen (lots of different places, so I can't even begin to try to cite for you) doesn't refer to garlic as a cure, rather as a preventative, as in humans, that boosts the immune system. That means it should be in their food regularly. NLS foods have it, and I haven't (knock on wood) had anything that could be traced back to parasites, and the of the fish deaths I have had in my tank, none have been in close proximity, chronologically speaking, to each other, so I doubt it was illness. Most of those deaths (only 1 had any indicators) were sudden, and 2 were jumpers, for a total of 9 deaths in about 2 years.