There is no real data or proof that garlic actually does anything for the health of the fish, but it is largely believed that it helps boost immune system and also acts as a appetite enhancer. From using garlic powder in the past with my fish, I believe that this is indeed the case. Whenever I add new fish or have fish that look like they may not be feeling well, or that arent eating, garlic soaked food seems to work like a charm, every time.