MEDICATIONS FOR FISH DISEASES
By Jim E. Quarles.
The entire purpose of drug therapy is that the drug or treatment be
effective against a parasite at a dose that doesn't hurt the host fish.
The drug must also be capable of being delivered appropriately, and that
often means injection or in the food.
There are a number of drugs effective when used as a bath, but there
few that the home aquarist can obtain that do any real and lasting good.
Now I will make a statement that will endear me to few if any
pharmaceutical providers for tropical fish treatments. Most are worthless
at best and can be killers in a lot of non informed uses. Most packaged
drugs offered via fish stores or aquarium shops, are inappropriate for
aquarium fish diseases, (a) it is used at an incorrect dose, ( b ) it is
expired ( has exceeded its shelf life), (c) for human or veterinary use,
(d) it must be ingested to be effective but is packaged for a bath, and
(e) it may be used indiscriminately as has been the case with antibiotics.
( I must avoid getting started about how stupid the average hobbyist is in
the use of antibiotics ).
To late, I have to state that far to many buy by the packaging and or
advertising and don't avail themselves of useful books or the services of
a veterinarian for advise about any given drug or antibiotic before just
plopping it into the tank. In fact, I have found from personal experience
that a very large number of hobbyist seem to enjoy mixing all the drugs
and chemicals they can buy and see how long their fish can withstand the
The object of any treatment should be to achieve a given result with a
given product over a given period of time, and know how you did it and be
able to explain it and repeat it. The people I have studied to a large
extent windup just making a chemical soup and hope the fins don't fall off
or the gills explode from the treatment.
Few medications have a documented history of effectiveness against
tropical fish disease organisms. The conclusions that are valid for cold
water salmon and trout and American warm water native catfish or
largemouth bass, are questionable when extrapolated to aquarium fish.
Also, few preparations sold over the counter to aquarists may be effective
in treating aquarium fishes because the drug doesn't have a target
parasite in aquarium fishes such as a gram-positive bacterial agent.
A lot of the bottles of chemicals sold contains a hodgepodge of
ineffective agents and colored water. They produce little effect, but
makes the hobbyist feel " well I have done something about this
diseased fish". Remember the company who packaged the product has one
set of goals and you another. They are selling the product to make money,
while on the other hand you are hoping against hope that they put
something in the product that will help at best and not kill your fish at
We do have several useful drugs as well, and competent companies
offering them in correct doses for the appropriate diseases, backed up by
substantive literature. When selecting a medication read the label, and
check out it's reported effectiveness in the literature of the trade.
Notable books listed in the references for this article should be in every
hobbyist's home library. They are not that costly when considering the
cost of replacing sick or dead fish.
CLASSES OF DRUGS OR CHEMICALS.
Among other highly effective drugs, formalin, malachite
green, copper sulphate and the benzimidazoles are defenses when dealing
with protozoans and metazoans that find their way into your tanks.
PRINCIPLES AND RULES OF USE.
There are many ways of treating fish diseases, one of which is the most
important; always treat fish in a separate, bare, hospital, or quarantine
tank with very strong aeration but no carbon filtration.
Always start with a smaller than recommended dose and increase the dose
gradually, watching the fish for indications of stress. For delicate fish
such as Discus you should decrease the dose and increase the temperature
in the quarantine tank, while maintaining hardness to protect the fish's
gills by providing calcium ions for osmoregulation.
Some manufacturers offer enhancers purported to increase the effectiveness
of almost any treatment. These should be considered with ( a grain of salt
) as far as their true value may be, in the treatment involved. Those
products that are " slime promoters " which provide a dressing
for wounds such as scraped, or scratched, or otherwise damaged skin or
gills of irritated fish, are highly recommended. I favor such products as
NovAqua, PolyAqua. These complexed water conditioners do a good job. They
should be used with all antibiotics, and added after harsh bathsof any
There are a number of dyes on the market that are highly effective in
treating parasites of tropical fish. However packaged dyes are not as
dependable as buying the powdered dye and preparing your own mixture. This
way you know the formula is fresh, and of the proper mixture for the most
effective cure. Malachite Green made from the zinc-free oxalate salt is
generally safe, but some fish are sensitive and can be easily killed
(tetras, catfish, and others.) It is never safe to use on baby fish. It
has proven to be effective against skin-gill-invading parasitic protozoa,
but becomes toxic in low pH soft water with increasing temperature, and so
it is not safe to just dump it into the tank using packaged directions.
Other dyes available to the hobbyists include acriflavine (used in
incubating eggs and treating cuts or bites and other skin damage. Then
there is the old favorite do nothing dye, called Methylene Blue. About all
this dye does is stain your aquarium sealant and darken the water.
The treatment of any thing with Methylene Blue is speculative at best.
However the use of Potassium permanganate which is a powerful oxidizer, is
very effective against many external parasites. Because of the oxidizing
nature of its reaction it should never be used with any other combination
of drugs or dyes. This product stands alone as a bath short term or long
term. Once you learn the proper methods for it's use it may prove to be
your best aide in treating external problems. I have found that using it
as a strong short term bath discus fish can be quickly rid of most
parasites and skin problems. Once again I must warn you this is not safe
with baby fish.
Malachite Green can be combined with formalin in an effective
antiprotozan therapy, but which should only be used with vigorous
aeration, since both tend to stress the respiratory system of fishes. This
dye will stain the silicone sealant of the aquariums and should not be
used in show tanks.