Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish


Red lined wrasse, Halichoeres biocellatus
Red lined wrasse, Halichoeres biocellatus


Hexamita is a flagellated protozoan disease which is often confused with Spironucleus. Spironucleus is responsible for what is commonly called hole in the head disease, Hexamita isn't.

Hexamita is a well known problem in cichlids which seem to be quite susceptible to it but it isn't just a cichlid problem, almost any fish can suffer from hexamita.
Hexamita is normally found benignly living in the fishes gut. If the fish are placed under stress their immune system can be compromised and opportunistic infections will occur because the hexamita is allowed to increase in numbers relatively unchecked and it is able to leave the gut and get in to the blood stream of the fish.
Each flagellated protozoa can reproduce just 24hrs after being born so once established in a host the disease is able to spread very quickly.

How hexamita begins

Hexamita is normally found in small numbers in the gut of fishes. When a fish is stressed due to overcrowding, shipping, poor water quality, bullying, wrong water chemistry and so on its immune system works less efficiently. This allows the hexamita to increase in numbers and move up from the gut in to the lumen of the upper intestine where it is able to swim freely in the intestinal fluids and eventually in to the bloodstream of the fish where it then spreads to the internal organs.

Symptoms of Hexamita

White stringy faeces is classic symptom of hexamita.

Infected fish lose their appetite and lose condition as a result, this makes the fish lethargic.

If the internal organs are affected, particularly the liver and kidneys the fish may lose control of its osmoregulation and show signs of dropsy.

Secondary bacterial infections of the skin are common in infected fish.

Occasionally swimming abnormalities can occur if the brain of the fish becomes infected.

Once established in an aquarium hexamita can reach such high numbers that new healthy fish added to the system will quickly be overwhelmed and succumb to the disease.

The fins of infected fish may lose the tissue between the rays of the fins making them look ragged.


Metronidazole at 50mg/l in a bath for up to ten days is usually effective. But this treatment will require the fish to be examined by a vet and the metronidazole acquired through a prescription in the UK

Water life - Octozin has been used to treat the disease successfully.

But there are over the counter remedies available which are effective because di-metronidazole has been made available to buy in fish keeping remedies through the small animal exemption scheme.

Once the hexamita has been treated the secondary infections will need treatment accordingly.

If the fish has suffered from dropsy to much damage may have occurred to the fish's organs due to the dropsy and its survival is less likely.

Treatment finder - for available commercial treatments


Dept. of large animal clinical sciences - Florida University.