There is no relationship between garlic's effect on bacterial infections and parasitic infestations. Also, the fish were not fed garlic-laced food; they were injected with garlic extract. That brings into question whether feeding fish garlic extract would be as effective as injecting them with it. Additionally, the garlic extract was prepared freshly for every injection. This is particularly important when taking into account the effectiveness of commercial preparation, and also in light of the fact that allicin, the active ingredient in garlic, is unstable and prone to breakdown in a relatively short amount of time (Cortes-Jorge 2000). Furthermore, since garlic is a non-natural food, the antigen effect of a novel compound may have been responsible for increased immune response, and although they used a negative control (nothing), they did not use a similar variable - i.e. onion, paprika, nutmeg, or whatever else one has in their spice cabinet that they think might somehow help their fish fight disease). And finally, even though all the fish showed improvement by the end of the study, none of the fish was completely healed. They all remained infected with Mycobacterium marinum, although at low levels.

You soak the food in the garlic juice, it boosts the fish immune system.

I have heard this mentioned a few times or here. I googled and got a bunch of conflicting data . So who on here feeds their fish garlic? and What does it do?

while many hobbyists report using garlic and then noticing an increase in feeding activity, there is no conclusive proof to this claim, either. It could be that the pungent and/or unrecognized/unnatural smell of the garlic brought the fish over to investigate the food, but there is no way of knowing whether or not they would have eaten food not treated with garlic, or whether or not any strong-smelling food additive would have done the same thing. It could also simply be that enough time had elapsed that the fish was finally prepared to eat and adding garlic was just a coincidence. Frankly, there are far too many variables to conclusively evaluate these claims

Taking these points in order, first garlic has never been conclusively proven to cure Marine Ich (Cryptocaryon irritans), ever. Some hobbyists have used it and reported that their fish got better, but these are not controlled studies and none of these hobbyists know for certain if their fish's own natural immunity was the true reason for the cure, or if garlic had any impact whatsoever. Also, there are a number of hobbyists which have used garlic and suffered significant losses of fish as well.

This brings me to my real point, which is that this highly flawed study is no better or worse than someone saying, "My fish would not eat. Then I added garlic extract to their food and they now eat great!" These reports are practically meaningless. Just as we cannot draw any conclusions from this public aquarium trial, nor can we draw any conclusions from similar unfounded statements made online