Diseases part 4

Diseases part 4


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 treatment.

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 its worst.

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.


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.


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 kind.


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.

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