For many years, garlic has been used to treat a number of diseases in humans ranging from bacterial infections to intestinal parasites. While the evidence for its effectiveness in man is largely anecdotal, there is now an increasing body of literature in the scientific journals relating to the antimicrobial properties of garlic. The main active ingredient of garlic is a compound called allicin. This compound does not exist in raw garlic, but is made immediately upon crushing or mincing the garlic clove, which mixes the allicin precursor with the enzyme required for its production.  Store bought minced, or crushed garlic, is rich in allicin. So, you may ask…what is the point of this post? Well, for the last 10 years or so, I have been using garlic prophylactically in my assorted reef systems to prevent protozoal infections of the fish. My methodology is simple. I mix crushed garlic (which I find in the refrigerated section of the deli aisle) with food pellets that I know my fish readily consume. I make an approximate 1:1 mix of pellets and garlic. I also pour some of the garlic juice into the pellets and allow the pellets to absorb the liquid. The mix is shook and stored in the refrigerator. The mix itself is moist, and in my experience, the Thera-A pellets manufactured by New Life are ideal as they do not disintegrate but retain their shape/texture for several weeks after mixing. The garlic particles take on a browner color from the pellets, as you can see in the pictures. Once made, the food mix is fed to the fish on a daily basis to keep potential parasites at bay.
Over the years that I have been doing this I have attempted to accrue evidence for its use and efficacy. I have to admit to the fact that my evidence is purely anecdotal, but I have done the following simple experiments…not at all scientific, but you can draw your own conclusion. Firstly, I would begin to feed garlic dosed pellets the first time I see symptoms such as flashing on the rocks or spots on the fish. This resulted in the symptoms clearing in a few days. However, one could argue that the disease had progressed through its life cycle and dropped from the fish…so no real evidence there. Secondly, I have withheld garlic when I would have otherwise fed it based on the symptoms above. This resulted in the symptoms remaining and/or increasing with more spots appearing (usually on my Regal and Powder Brown tangs). Then we come to the third line of evidence. When I can no longer bear looking at the fish flashing the rocks, I begin to feed garlic. Within 2 days, there is a significant increase in the fish health and by 4 days, the fish appear asymptomatic. Judging by the speed that garlic therapy appears to work, I strongly suspect that the allicin is secreted into the mucus coat of the fish, potentially concentrating it at the site of fish/parasite interaction.
So- the evidence is anecdotal at best- but I have repeated this many times. In a tank such as mine that contains lots of tangs, the potential for an out break of protozoal disease is always a constant concern. Do I think garlic helps with this ? Absolutely. Does it bother the fish? Not at all. In fact, I would go as far as saying that my tangs and pink tail trigger actually seek out the garlic in the pellets. It has long been known that adding garlic in food preps can really help stimulate the appetite of finicky feeders, so chances are your fish will readily accept this food blend. If there is a down side- some varieties of macroalgae will metabolize components in garlic and produce a somewhat “odd†almost sulfurous aroma for a while after feeding the tank, but to me, that is a small price to pay for healthy fish.
I mentioned earlier that garlic is receiving much attention in the scientific literature. A simple web search for “allicin antimicrobial†will result in a mass of reference material you can wade through, however this minireview and manuscript by Harris et al. provide a great deal of insight into the potential of garlic therapy.
