Intestinal flagellates

In addition to the normal bacterial flora, the fish intestines also contain flagellates, which do not cause disease if the immune system is healthy. If the fish is weakened by various stressors, various symptoms can occur.

Definition of the disease

If the intestinal flagellates multiply very strongly, an inflammation of the intestinal mucosa develops. The fish excrete mucilaginous, whitish faeces, the anus is reddened and inflamed. The abdomen is distended. Due to the reduced feed intake and the loss of nutrients through diarrhoea, the fish quickly lose weight. The skin turns dark. Due to the lack of minerals, the cartilage in the head area recedes. White holes develop (hole disease) The animals swim jerkily. They appear tired and separate themselves from the other fish.

Symptoms with a Intestinal flagellates Infection

  • mucopurulent ooze
  • distended stomach
  • Emaciation
  • reduced feed intake
  • white holes in the head area


Intestinal flagellates are unicellular flagellates, with 1 or 2 cell nuclei, which feed on bacteria in the fish’s intestines. Their locomotion takes place through two thread-like projections (flagella). If the fish is stressed by poor husbandry conditions, such as incorrect water temperature, unfavourable pH value or inferior food, the flagellates multiply and damage the intestinal wall. Overstocking and a too low oxygen content of the water promote the outbreak of the disease. It is a factor disease. The intestinal flagellates are excreted with the faeces and infect the other fish in the aquarium.

Infestation with intestinal flagellates must be distinguished from a disease caused by inferior food. A too high content of carbohydrates and a too low amount of roughage in the fish food causes similar symptoms and also leads to a reproduction of the flagellates.

Intestinal flagellates in fish

  • Spironucleus
  • Hexaminta
  • Trichomonas
  • Bodomonas
  • Protoopalina


The damage to the intestinal wall means that not enough nutrients can be absorbed. The stomach collapses. Due to the storage of liquid or air deposits, the abdomen is distended in some places. Since parts of the intestinal mucosa are also excreted with the faeces, the faeces draw mucous threads. Harmful bacteria begin to multiply in the intestine and increase the inflammation of the mucous membrane. If the intestinal flagellates enter the kidneys and liver with the bloodstream, severe organ damage occurs. Without treatment, the fish die within a few days.


1. high-quality lining

To prevent the formation of holes in the head area, high-quality food and a vitamin and mineral preparation must be fed immediately.

2. Optimisation of the aquarium water

The water of the aquarium is changed before treatment with medication. A slow increase of the temperature to 35 degrees Celsius supports the treatment. The nitrate value of the water should be controlled.

3. Medication

If intestinal flagellates are detected during a microscopic examination, all fish in the aquarium must be treated.

Sera Flagellol

1 ml of the medicine is mixed in 40 ml of water. During the treatment period of 3 to 7 days, the water must not be irradiated with UV lamps or cleaned with activated carbon filters.


Nitrothiazole-amine and other active substances kill the intestinal flagellates and encapsulated cysts on the aquarium floor.


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