Hole In The Head (hexamita)

Hole In The Head (hexamita)

Hole In The Head (hexamita) Discus

Hole In The Head (hexamita) is a protozoan parasitic infection that appears as lesions on the head and flanks of freshwater and marine fish.   The lesions are caused by Hexamita parasites that migrate into the sensory pores on the head of the fish where they cause the surrounding tissue to decay.   Because of the large amount of damage to the epidermis, secondary infections often set in making things worse.


Other than the obvious “hole in the head”, additional symptoms include the following:

  • Listlessness, restlessness

    Hole In The Head (hexamita)

    Hole In The Head (hexamita)

  • Emaciation, weight loss
  • Darkened body color
  • Pale or reddish looking patches on the skin
  • Copious amounts of stringy pale white feces
  • White slime discharge caused by irritation of the intestine wall
  • Pitting and erosion of skin and muscle tissue around the face and body


The Hexamita parasite is present in low levels in the intestines of many aquarium fish where they present no problems, however, when the immune system of a fish is weakened in some way, the parasite begins to rapidly multiply and spread to the other internal organs causing the fish to die.

Poor water quality, inadequate diet, and poor aquarium maintenance are the primary cause associated with Hole In The Head disease.


The premiere medication used to treat hexamitiasis is metronidazole; known by the trade names General Cure Freshwater & Saltwater Aquarium Parasitic Fish Disease Treatment By API, Fish Zole™ from Thomas Labs, MetroPlex™ from Seachem, Flagyl, etc.

In early stages of the infection where the fish is still eating, the most effective approach is to feed medicated fish food infused with metronidazole.   Mix 1 gram with 100 grams of food and feed the mixture for 4 or 5 days.

When the fish is not eating, add the medication directly to the tank water at a dosage of 250 mg per 10 gallons, once a day, for at least three days. After three days make at least a 50% water change with carbon filtration for a minimum of 24 to 48 hours, or perform a complete water change. Metronidazole can cause damage to the kidneys and other internal organs over extended periods and must be removed from the tank water.

Dimetridazole is also used by some tropical fish keeping enthusiasts to a lesser degree with less satisfactory results.

After the medication has been removed from the tank, improvements to water quality and diet are absolutely essential.


Hole In The Head disease (hexamita) is an accumulation of poor water quality, an unbalanced diet, and the parasite itself. To prevent the occurrence, maintain the following:

  • Pristine water conditions by performing frequent, regular, water changes
  • Avoid abrupt fluctuations in water temperature
  • Avoid introducing new fish without first quarantining them
  • A varied, balanced diet with occasional live foods

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