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Garlic for Marine Fish - Part I (posted by Humaguy)

Posted 02/27/2014 at 04:46 PM by snorvich
Updated 03/18/2014 at 05:37 PM by snorvich

I recommend you avoid garlic, I stopped using it....

OK I'm a no garlic for marine fish person.
Well firstly let me give you a little background on where Iím coming from, Iím a fish disease research scientist and I specialize in fish vaccination and ectoparasite infections in fish. I don't work for, sell or am I in anyway assciated with commerical fish food production. My research laboratory has carried out many trials for fish feed manufactures on garlic, both as an appetite stimulator, immunostimulant and white spot ďcureĒ and I shall link to some of this work published on UR and in the scientific literature.
So why not use garlic in marine fish diets.
1 Long term heart and liver lesions
Terrestrial plant lipids are well known to cause heart and liver lesions in marine fish. The problem with feeding terrestrial plant oils (not just garlic but any terrestrial plant oil) to reef fish is problematic due the nature of the lipids the fish do not possess the enzymes to digest them correctly and this leads to fatty deposits and serious pathological changes in the heart and liver of fish that are fed these lipids. Although these are not instantly fatal they cause chronic change to these organs and long term deterioration in the health of the fish. Granted much of this his work is done on farmed fish, but it is a well known phenomena and here are some of the research papers that detail this problem.
AH, Sargent JR, Thompson KD 1993
Terrestrial and fish oils affect phospholipid fatty acid composition, development of cardiac lesions, phospholipase activity and eicosanoid production in Atlantic salmon (Salmo salar).
Prostaglandins Leukot Essent Fatty Acids. 49(3):665-73
AH, Park MT, Sargent JR.1991.
High dietary linoleic acid affects the fatty acid compositions of individual phospholipids from tissues of Atlantic salmon (Salmo salar): association with stress susceptibility and cardiac lesion.
J Nutr. 121(8):1163-72

J. Gordon Bell2, John McEvoy3, Douglas R. Tocher, Fiona McGhee, Patrick J. Campbell* and John R. Sargent 2004
Replacement of Fish Oil with Rapeseed Oil in Diets of Atlantic Salmon (Salmo salar) Affects Tissue Lipid Compositions and Hepatocyte Fatty Acid Metabolism
The American Society for Nutritional Sciences

J.G. Bell1, D.R. Tocher1, B.M. Farndale1, A.H. McVicar2 and J.R. Sargent1 1999
Effects of essential fatty acid-deficient diets on growth, mortality, tissue histopathology and fatty acid compositions in juvenile turbot (Scophthalmus maximus)
Journal Fish Physiology and Biochemistry 1573-5168 Volume 20, Number 3 p263-277

SL Seierstad, TT Poppe, EO Koppang, A Svindland, G 2005
Influence of dietary lipid composition on cardiac pathology in farmed Atlantic salmon, Salmo salar L
Journal of Fish Diseases.

These scientific journals detail the pathology and chronic changes due to these lipids (there are many more) but there arenít any on reef fish, mainly as they are not a major farmed species or laboratory model, however if you apply the precautionary principal to your fish (in the same way it is applied to Humans) then you wouldnít feed your marine fish diets containing terrestrial lipids. This has a human health comparison with Trans fats, very useful in making vegetable oils butter like so common in vegetable spreads and thought to be harmless until it turns out they cause liver tumors & heart disease in rats and mice and probably in humans too. So if this evidence is good enough to ban trans fats in foods then the much stronger data in fish should be good enough to ensure you donít feed terrestrial oils to reef fish. As I said earlier my lab (which is a fish health research lab at a leading University) is often asked to carry out feed trials for feed manufactures and we have carried out many that use garlic or garlic extracts. Unfortunately these are considered to be commercially sensitive and I cannot tell you the results of using them to control white spot (but suffice to say the companies we have carried out scientific trials have all decided not to launched garlic supplemented feeds). However I did persuade one feed manufacturer to allow me to post the growth data from their feed trial on UR. The results were, well, damning for garlic. Here is the link to the trial from my lab in this thread (

Why do manufactures put it in their food? well clearly there is a demand for it and they are supplying that market demand. It doesnít mean it good for your fish it just means that they will sell more of their food if people are misinformed and think it is beneficial

2 Garlicís Anti-parasitic Properties

The first question I have is please show me a research paper with proper controls where garlic has been shown to cure parasitic diseases in fish. Iíve just visited web of Science (a major research database) and there are no research papers that do this.

Much of the anti parasitic effects of garlic are attributed to Allacin and most work is done in humans, where it may have some benefits if purified allacin is fed, at around 400mg kg/bw every day. However in many mammals, (dogs, cats, horses etc) garlic causes a Heinz body anemia which is potentially fatal.

My laboratory has recently carried out a trial using purified allacin in clown fish

I recently picked up a MAEFS grant to look at this and the preliminary results are as follows The experiment was as follows

90 clown fish 40 on allicin, 40 not, 10 time zero samples. 10 sampled per week per group. The dose of allacin is 400ug/kg bw (a level used in humans and about 400ng/fish)

week 0 mean both groups 41.7% Hcrt
week 1 test 34.7% Hcrt control 42.4% Hcrt
week 2 test 18.8% Hcrt Controls 41.% Hcrt
week 3 test 17.2% Hcrt Controls 42.8% Hcrt
week 4 test 17.0% Hcrt Controls 40.6% Hcrt

Hcrt= haematocrit (how many red cells there are in the blood). The histology results on the organs hasn't been processed yet

Clearly allacin causes acute Heinz body anemia in reef fish too

To assume that all fish can eat garlic with no ill effects seems optimistic, when in mammals (which as a group are far more closely related to each other that fish are) it is fine for some e.g. the great apes, but toxic for dogs and cats (see O. Yamato, E. Kasai, T. Katsura, S. Takahashi, T. Shiota, M. Tajima, M. Yamasaki, and Y. Maede Heinz Body Hemolytic Anemia With Eccentrocytosis From Ingestion of Chinese Chive (Allium tuberosum) and Garlic (Allium sativum) in a Dog J. Am. Anim. Hosp. Assoc., January 1, 2005; 41(1): 68 - 73. (which is just one of 100's of research articles on this in the field))

3 Well Garlic must be an immunostimulant

In the most recent review if immunostimulants in marine fish

Ian Bricknell & Roy A. Dalmo 2005
The use of immunostimulants in fish larval aquaculture
Fish & Shellfish Immunology 19 (5) 457-472

Garlic is not referred to as an immunostimulant.

To be honest garlic has been discussed many time on UR, if you want to feed your fish garlic then nothing is stopping you, but I doubt you will see a benefit and the evidence strongly suggests you will do short and long term harm to them.
If all a new hobbyist were to do was gloss over the medicine aisle at his favorite local fish store and observe the proliferation of garlic-based treatments, or peruse the various online postings of garlic's proponents, he would surely come away with several likely impressions:

Marine Ich/Cryptocaryon irritans (and just about anything else) is easily cured by feeding garlic.

Quarantine tanks are an unnecessary expense and hassle (assuming he has even heard of a quarantine tank).

Garlic is a proven appetite stimulant, which can compel even challenging-to-feed fish to take prepared foods.

Garlic must assuredly be a proven method of disease treatment. Why else would so many reputable manufacturers make and market a cure if it had not been scientifically proven?

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.

Second, quarantine tanks are a cost-effective and simple method to ensure the health and well being of your aquatic pets. These tanks really should be standard in this hobby and it is a real shame that they are so often overlooked. In my opinion, stores and fellow, experienced hobbyists who don't recommend this protocol to beginners are doing them and the hobby in general a disservice. Advocating that aquarists play it fast and loose when it comes to quarantine is frankly irresponsible and is likely setting them up for eventual failure.

Third, 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.
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