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
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.
And regarding the last point above, so many manufacturers
are making these products because there is market demand for
them, plain and simple. A lot of people are buying garlic-based
medications, so the manufacturers are simply giving the buying
public what it wants. The list of manufacturers that have
jumped onto this bandwagon is truly impressive. Just about
every major manufacturer is marketing its own brand of garlic
extract. A quick search of a couple of my local fish stores
yielded the following:
Ecosystem Garlic Elixir
Kent Garlic X-treme
Seachem Garlic Guard
Various brands of fish food are now even promoting that they
have added garlic to their recipes. And yet, none of these
alleged benefits has ever been proven. That is not to say
that no studies have been done on garlic and its use to combat
fish diseases. Several studies have been published regarding
garlic, but none of these has dealt with Cryptocaryon irritans,
which seems to be the most common ailment for which garlic's
use is advocated, likely because it is simply the marine ornamental
disease most commonly encountered.
From left to right: some fresh garlic, Ecosystem's Garlic
Kent Marine's Garlic Xtreme, and Seachem's Garlic Guard.
Garlic by Any Other Name Still Smells Just as
garlic in a number of different ways. The most common is simply
to say they treated the food with garlic or garlic extract.
Those are both easy enough to understand. But, various references
also use other names. The scientific name for the garlic plant
is Allium sativum, so don't be confused if that name
comes up when reading other articles or any of the references
listed at the end of this article. Some people also use the
term allicin. That is shorthand for the active ingredient
in garlic extract. Chemically, allicin is diallyl thiosulfiniate
or diallyl disulphide-oxide (Cortes-Jorge
2000). All of these terms, though, are generally talking about
the same thing.
Garlic as an Appetite Stimulant:
I was able to find
one brief report from the public aquarium literature that
attempted to use garlic extract as an appetite stimulant (Ashdown
& Violetta, 2004). This "experiment" was conducted
at SeaWorld in Orlando, Florida. A 660,000-gallon display
containing 50 assorted elasmobranchs was the test tank. It
held 19 sand tiger sharks (Carcharias taurus). Of those
19, two of the sharks had refused to eat regularly and had
begun to lose weight over time. Sand tiger A once weighed
in at 108 kg in 1990, but by April 2003 was down to 73 kg.
Sand tiger B was its largest in March of 2002, weighing 74.5
kg, but had also decreased in size and weighed only 70.6 kg
in April of 2003.
At that point, each shark's food received
garlic added in the ratio of 1 cc of minced garlic per pound
of food offered. They were then fed the garlic-laced food
for 13 weeks. Sand tiger A took to the treated food immediately
with new vigor. It ate near or above its targeted allotment
of food every day during the testing but one. And on that
day, the shark had been weighed, so the SeaWorld personnel
felt it was possible that the stress of the procedure affected
its appetite. But, sand tiger B did not demonstrate the same
change in behavior. It refused to eat at all for the entire
first month of the testing phase. And when it did finally
eat some of the garlic injected food, its feeding behavior
did not improve and it continued to feed only sporadically.
All in all, this brief report is certainly
not a ringing endorsement of garlic as an appetite stimulant.
That said, there are numerous problems with this study. First,
from our perspective as aquarists, they made this attempt
with sharks and not standard aquarium fishes. Second, they
used only two test subjects. A larger group of fish would
be best for comparison. And finally, there were no controls
to speak of. Since we cannot discount some other factor having
been involved in sand tiger A's behavioral changes, we really
can't draw any conclusions from this report.
This brings me to my real point, which is that this highly
flawed study is no better or worse than someone saying, "My
fish would not eat. Then I added garlic extract to their food
and they now eat great!" These reports are practically
meaningless. Just as we cannot draw any conclusions from this
public aquarium trial, nor can we draw any conclusions from
similar unfounded statements made online.
Garlic Versus Mycobacterium marinum:
Garlic has been
studied for its effectiveness against a bacterial infection
of fish (Colorni et al, 1998). One hundred and sixty
sea bass (Dicentrarchus labrax) were intentionally
infected with Mycobacterium marinum via injection with
cultured cells. The study's participants also kept a positive
control group of another 40 specimens, which they held in
conditions similar to, but separate from, the infected fish,
but injected them only with saline. All of these fish were
then held and monitored to watch the disease's progression.
After nine weeks, the infected fish showed clinical signs
of infection upon dissection and examination. At this point,
the infected fish were broken up into four smaller groups
of 40 each: a negative control group which received no treatment,
an experimental group that received antibiotic (streptomycin)
injections, a second experimental group that received garlic
extract injections, and a third experimental group that received
injections of both the antibiotic and garlic extract. All
fish were treated for an additional 12 weeks. During this
time, sample fish were selected and dissected to monitor the
disease's progression or recession.
The interesting revelation that came from
this study is that it revealed a statistically significant
stronger immune response in the fish given only garlic versus
the fish given antibiotics, antibiotics and garlic, or the
untreated control group. Part of this apparent anomaly is
that antibiotics also have an immunosuppressive effect. In
layman's terms, while they work to kill bacteria, they also
don't permit the body to fight as hard as normal against the
infection. But, the fact that the fish treated with garlic
showed a stronger immune response than the untreated control
group lead the study authors to suggest that "allicin
treatment seems to have an enhancing effect on antibody activity
when compared with all other groups."
A Heniochus butterflyfish in a reef display with
the tell-tale spots of a marine Ich (Cryptocaryon
irritans) infestation. Because of the perceived
difficulty in removing sick fish and because so few
hobbyists follow quarantine protocols, a lot of aquarists
are 'experimenting' with garlic and keeping their fingers
The bad news is that this paper dealt with
a bacterial infection. There is no relationship between garlic's
effect on bacterial infections and parasitic infestations.
Also, the fish were not fed garlic-laced food; they were injected
with garlic extract. That brings into question whether feeding
fish garlic extract would be as effective as injecting them
with it. Additionally, the garlic extract was prepared freshly
for every injection. This is particularly important when taking
into account the effectiveness of commercial preparation,
and also in light of the fact that allicin, the active ingredient
in garlic, is unstable and prone to breakdown in a relatively
short amount of time (Cortes-Jorge
2000). Furthermore, since garlic is a non-natural food, the
antigen effect of a novel compound may have been responsible
for increased immune response, and although they used a negative
control (nothing), they did not use a similar variable - i.e.
onion, paprika, nutmeg, or whatever else one has in their
spice cabinet that they think might somehow help their fish
fight disease). And finally, even though all the fish showed
improvement by the end of the study, none of the fish was
completely healed. They all remained infected with Mycobacterium
marinum, although at low levels.
I wonder if this could this be why some
people who don't use conventional, proven treatments such
as hyposalinity and copper see repeated outbreaks when adding
new fish or when their current fish become stressed? The idea
that garlic could possibly help with a stronger immune response
but not completely eliminate the pathogen is intriguing to
me. This would help to explain some of the posts on the internet
message boards of repeated outbreaks as well as provide false
evidence to the believers that Marine Ich/Cryptocaryon
irritans is always present. That theory aside, I have
already stated that bacteria are completely different than
parasitic protozoans. There maybe no correlation at all. It
is simply something that struck me in my reading.
There is also one more problem with this
study. When they began, they believed that they had naïve
fish, ones that had never been exposed to Mycobacterium
marinum. But, as the study progressed and additional tests
were undertaken, they later believed that the fish had had
some previous exposure to this pathogen because of antibody
counts in the unexposed control group.
Sodium Percarbonate and Garlic Versus Ichthyophthirius
paper (Buchmann, Jensen, & Kruse, 2003) detailed work
done with sodium
percarbonate and garlic extract against Freshwater Ich/Ichthyophthirius
multifiliis. The push for this study involved malachite
green, a substance routinely used to deal with this parasite
that was banned for use on food fish because it is carcinogenic.
So, safe yet effective alternatives were being investigated.
This study was strictly an in vitro
trial. Basically, parasites were harvested, placed into Petri
dishes, exposed to sodium percarbonate or garlic extract,
and then monitored to determine the lethal concentrations
and exposure times of both. The study found that sodium percarbonate
killed the free-swimming infective stage of Freshwater Ich/Ichthyophthirius
multifiliis at 12.5 mg/L for 180 minutes or 62.5 mg/L
for 90 minutes. Garlic extract required 62.5 mg/L for 900
minutes or 312.5 mg/L for 180 minutes to be effective. For
comparison, malachite green is effective in 90 minutes at
only 0.5 mg/L or 900 minutes at 0.1 mg/L, much lower concentrations
than either of the experimental treatments. For the parasite's
reproductive cyst stage, no concentration of sodium percarbonate
was noted that differed from the control in effectiveness,
while it required 570 mg/L of garlic extract to kill 100%
of the cysts. Again, for comparison, only 0.15 mg/L of malachite
green is needed to kill 100% of the cysts.
Even major fish food manufacturers have jumped on the bandwagon
promoting their formulas with garlic added.
That all said, like the other two experiments
I discussed, there is little that we can conclude from this
paper, either. First and foremost, Freshwater Ich/Ichthyophthirius
multifiliis and Marine Ich/Cryptocaryon irritans
are not very closely related (Colorni & Burgess, 1997).
While it is obvious to anyone familiar with scientific names
that these two parasites are in different genera, they are
also in totally different classes, with Freshwater Ich/Ichthyophthirius
multifiliis being in Oligohymenophora, order Hymenostomatida
and Marine Ich/Cryptocaryon irritans placed in Colpodea,
order Colpodea. While these two ectoparasites share an apparently
similar lifecycle and dispersal mechanism, these similarities
are likely caused by convergent evolution rather than by having
evolved from a close common ancestor.
As further evidence of the difference between
these two parasites, note that malachite green, the medication
that the researchers were seeking to replace, is very effective
against Freshwater Ich, Ichthyophthirius multifiliis,
but is generally not recommended for use against Marine Ich,
Cryptocaryon irritans. So whether or not garlic is
ever proven to be effective against Freshwater Ich, it does
not automatically follow that it will be equally effective
against Marine Ich. In fact, there is no a priori reason
at all to expect that any medication effective against one
of these parasites would also be effective against the other.
Second, this study was only the first step with in vitro
experiments. These drugs were not tested on affected fish.
It could be that these drugs at these concentrations do work
against the parasites, but could also be deadly to the fish.
For example, other experiments on saltwater fish infected
with Marine Velvet, Amyloodinium ocellatum, showed
that hydrogen peroxide was effective in ridding the fish of
the parasites, but it also induced mortality rates of anywhere
between 30% and 100%, depending on the amount used and the
subject being tested (Montgomery-Brock et al, 2001
Clearly, this illustrates the importance of finding a treatment
that works against the target organism but doesn't endanger
the host fish.
Now, I understand that many are going to argue that garlic
is natural, so regardless of its concentration, it should
be safe. My response is simple: palytoxin is natural as well.
So is lionfish venom. A lot of naturally occurring substances
are harmful, even deadly. Just because something is natural
does not automatically render it safe.
Finally, because this was an in vitro trial, the garlic
extract was not fed to the fish, as there were no fish to
feed. The extract was simply added to the water and it was
noted whether or not it had an effect on the parasite's cyst
or free-swimming stages. This raises yet another question
of whether or not garlic extract in food would be effective
Garlic Versus Intestinal Worms:
One article (Fairfield,
1996) that I found details an experiment conducted using garlic
extract to combat a nematode (Capillaria species) infestation
in common freshwater angelfish (Pterophyllum scalare).
The author of this article went to various breeders, wholesalers
and retailers looking for angelfish in which this worm was
present. Suspected host fish were given a colonic wash to
look for evidence of worms and/or their eggs. From a wholesaler,
sixty individuals were selected for this study that were described
as having a "moderate to heavy load of these parasites."
These 60 fish were divided into two groups. From each group,
five individuals were randomly selected, killed and dissected
to examine the number of worms and eggs present. An average
of 2.1 worms per fish was found in the dissected fish along
with an average of 10.3 eggs per fish. The remaining 25 fish
from each group were given another colonic wash. The author
found that these fish had an average of five eggs per fish,
but no worms were extracted during the colonic wash procedure.
Both fish groups were housed in identical 55-gallon aquariums.
They both were fed a homemade fish food recipe, but the experimental
group had fresh garlic extract added to its food. The fish
were held for two months, with half receiving the garlic-laced
food. After that time, all the fish were euthanized and dissected.
Of the experimental group, all of the fish but two showed
a complete absence of any worms or eggs. One fish still had
one worm, while the other one had eight. Neither fish had
any eggs present at that time. The one fish that still had
eight worms was noted as being the smallest of the group.
It was theorized by the article's author that being low in
the pecking order had contributed to this particular fish's
not getting enough to eat, and therefore possibly not ingesting
a sufficient quantity of the garlic to make a difference.
In contrast, the untreated control group had an average of
two worms and 14.6 eggs per fish upon dissection. This would
seem to show that garlic can be used to treat nematode infestations
in freshwater angelfish.
But this study, like the other ones, has some problems. Foremost,
a number of the fish from each group, 12 from the experimental
group and 11 from the control group, died prematurely. This
stopped the author from completing a statistical analysis
of the study's results. These fish all apparently suffered
from a ruptured lower intestine from the colonic wash procedure;
in short, death by enema. Quick poll question; how many of
you all are shifting uncomfortably in your seats or clenching
tightly as you read this? These deaths reduced the total number
of study participants to the point at which "a definitive
conclusion on the effectiveness of garlic cannot be made."
Additionally, this study, like several of the others, also
used fresh garlic. This again begs the question of whether
or not commercial preparations are going to be effective after
being processed and then sitting on a shelf for an undetermined
amount of time at distributor, wholesaler and retailer locations.
And along those same lines, what type of 'fresh garlic' are
people using? I imagine just like all other commercially grown
crops, garlic too has been selectively bred over the decades
to develop varieties that differ in taste, texture, size,
smell, etc. I don't believe whether or not the variety of
garlic used affects the allicin concentration has been investigated.
And lastly, these were freshwater fish. There is no telling
whether or not these results (if later repeated, analyzed
and statistically verified) would hold true for all susceptible
species of saltwater fish or all the potential intestinal
parasitic worms that they carry.
Kelly Jedlicki's Western Marine Aquarium Conference
To properly discuss
the use of garlic, we really need to go back to the origins
of garlic's use for ornamental marines and revisit the presentation
Kelly Jedlicki gave at the 1998 Midwest Marine Aquarium Conference
in Michigan. It was there that the idea of feeding our fish
garlic was first introduced to the saltwater hobby. Now, I
must admit, I was not lucky enough to attend this conference
firsthand. But, I know Kelly rather well now, and we have
discussed this topic on numerous occasions.
Kelly was giving a presentation on general pufferfish care.
Part of her discussion centered on the number of fish that
she had received that were parasitized with internal worms.
In looking for a treatment that was safe and effective, she
stumbled across garlic. At this conference, she shared her
anecdotal experience of garlic being an effective dewormer.
She also happened to mention in passing that she noticed a
general decrease in occurrences of Marine Ich/Cryptocaryon
irritans when using this garlic treatment. That's it.
This does not sound like a ringing endorsement to me. Nor
was this a controlled study demonstrating that garlic had
an effect on Marine Ich/Cryptocaryon irritans. But
none of that seems to matter because from there the legend
of garlic spread far and wide. Why are so many people willing
to go with this "treatment" based solely upon this
one innocuous, anecdotal report? I hate to say it, but I believe
laziness had to play at least part of a role. Consider the
alternative, proven treatments for an infected tank. In the
lack of an easily available magic bullet, the hobbyist has
to tear apart the entire aquarium, remove all the fish to
a second quarantine system and treat them with hyposalinity
or copper while leaving the display empty of fish for a month
or two. Or, the aquarist can simply leave the fish in the
display and add a couple of drops of this garlic extract to
their food and they should heal on their own. When put in
those terms, who wouldn't pick the garlic alterative?
To recap, garlic's
use as an appetite stimulant is questionable at best. It seemed
to have a positive effect when injected into fish that were
infected with a bacterium. It can kill the freshwater Ich
parasite Ichthyophthirius multifiliis when dosed in
rather high concentrations in the water. And, it might be
an effective dewormer in freshwater fish. But, none of that
means it will do anything against Marine Ich/Cryptocaryon
irritans when added to the food of infected fish.
So, now that we know what has been studied regarding garlic,
it should be readily apparent that there is still much that
we don't know about garlic's use as a treatment, particularly
against Marine Ich/Cryptocaryon irritans. I hope to
shed some light on this in the coming months with a controlled
study testing the effectiveness of garlic extract on fish
exposed to Marine Ich/Cryptocaryon irritans. Hopefully,
I will be able to determine whether garlic has any effect
against this parasite, independent of natural acquired immunity.
Until such time as that is proven, use a garlic treatment
at your (and your fishes') own risk.