If you want to end the anecdotal reports and instead consider the science on this I suggest you go here:
https://scholar.google.com/
The enter "Garlic in fish food" You should get "About 147,000 results (
0.10 sec)" Of cpurse you cannot read them all but you can skimm through a few pages and get the gist of the general sentiment. Most of the ones I looked at in the first few pages were pretty pro-garlic and they explained why.
For GaryE
Afifah, D., Arief, M. and Al-Arif, M.A., 2021, February. The effect of garlic (Allium sativum) and turmeric (Curcuma longa) extract addition in commercial feed on feeding rate, feed efficiency and feed conversion ratio of gouramy fish (Osphronemus gouramy). In
IOP Conference Series: Earth and Environmental Science (Vol. 679, No. 1, p. 012073). IOP Publishing.
Abstract
Gouramy is known to it’s low appetite and slow growth. Attractants are ingredients that are mixed in small amounts of feed to increase feed intake, growth, and fish consumption of feed. Garlic contains at least 33 sulfur components that give a distinctive odor and various medicinal effects. Turmeric contains essential oils composed of monoterpenes and is an effective odor stimulating precursor compound used as an attractant. This study aims to determine the effect of giving turmeric and garlic extracts at different doses on feed consumption, feed efficiency and feed conversion ratio in gouramy. This study used an experimental method with 5 treatments; P0= control, P1=1% garlic extract addition, P2= 1.5% garlic extract addition, P3= 1% turmeric extract addition and P4= 1.5% turmeric extract additions with 4 replications using 10 fish in each.. The results showed that the highest feed consumption value was in the treatment of P1and P2, the lowest conversion ratio and the highest value of feed efficiency was found in the treatment of P2 and P3. So it can be concluded that the addition of 1.5% garlic extract or 1% turmeric extract is effective as an attractant and effective for increasing the growth of gouramy.
(edited to spell fish properly- DOH!)