All I know is garlic is easily injected into earthworms, and is a natural solution for attempting to treat and stimulate sensative fish such as stingrays.
In my experience, a particular Castexi was not eating very much and was not producing healthy looking feces.. After a week of injected earthworms, it began to put on weight, show darker coloration around the disk, and produce long, single, solid peices of feces.. This same ray is now a healthy 16-17" across! But upon importation, his health could of been questionable.
It is also known that a large group of South American Puffers never perished due to any sort of internal problems, as they were initially treated with a garlic extract. Often times, wild imported Puffers will have a serious internal parasite problem, in which we lost maybe 1 or 2 of a group of 50. Could be coincidence, but the previous batch of Puffers did not even make it out of our exporters facility due to the fact they were dropping in large numbers on a daily basis, before treatment.
I have also had finicky eaters who had refused to eat prior to soaking food with garlic, only to devour it afterwards. It is also a good 'tool' in order to convince predators that 'Fish Injcted with Garlic' is the same food source as 'Shrimp Soaked in Garlic'.. They smell it, they taste it, they eat it. It worked for my Lionfish.