Mr. Hexamita

Mr. Hexamita



By Jim E. Quarles

If you keep discus fish sooner or later you're going to have this unwanted guest appear in your tank and cause your beautiful discus all kinds of grief. I am sure you have seen programs about Americas TEN MOST WANTED CRIMINALS by the F.B.I.!

Well, Mr. Hexamita is either # 1 or close to it on the unwanted list for discus diseases. But despair not, there is a way to lock this criminal out of your fish.

This is a parasite caused problem. A flagellate protozoan, called Hexamita, also known as Octomitus. The obvious symptoms are easy to spot. Small holes appear in the body, especially the head region, which develop into tubular eruptions.

Most of the time yellow, strings of mucus will be seen coming from the lesions. This leads some hobbyist to mistake this parasite as a worm infestation. Lesions may also develop at the base of the fins and near the lateral line.

Photo credit to Tetra Press

Affected fish will go off their food and become hollow bellied, this increases the weakness of the affected fish and other diseases may develop in short order. Hexamita exists as a low level infection in the intestines of cold water and tropical fish. It should be noted that it is noticed in most cichlids.

Quite a few factors may come into play with causing the onset of this disease, over crowding, low oxygen content of the water, when you find this disease most often you will also note unhygienic conditions in the tank. Even quick changes in temperature and poor diet can cause the latent parasites to multiply and develop the acute symptoms.

It is my feeling also that a lack of vitamin C & E play a part in the development of this problem, as well as environmental factors.


The best way of treating hole in the head disease is with medicated food. But it is sad to say, affected fish often stop feeding and it is difficult to mix medicated food on a small scale.

However there are a few drugs that can be mixed into the treatment tank's water that have proven effective, Dimetridazole and Metronidazole, both of which are only available with a veterinarian's prescriptions in certain countries.

For long term control it is important to quarantine all new stock, and give appropriate preventative treatment and eliminate the factors which are known to bring the onset of this disease. I would recommend fresh vegetable matter in the diet and removing activated carbon during treatment.


Most people fail to realize that most apparently health fish are usually carrying a wide range of potential fish pathogens in or on their bodies at all times.

These are latent infections that do very little harm, but their importance to the fish keeper cannot be over looked. Even under the best conditions and with the healthiest fish, lurks pathogens just waiting to cause problems for the less than vigilant hobbyist.

I hate to bring this matter into this article, but it must be said or go unnoted. Breeding hybrids can interfere with and weaken the immune system of all fish. This hybridization is most noted in the current crop of discus being kept by most discus hobbyist. So it is possible that the fancy color morph's, desired by so many are going to be victims of this and other diseases to a much greater degree than the wild stock of yester-year.

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