White spot disease / Ichthyo / Ichthyophthirius multifiliis

The white spot disease, also called ichthyo “ich” / Ichthyophthirius multifiliis or just spot disease, is widespread among freshwater fish. It mainly affects fish that are already ill or stressed and whose immune system is disturbed.

Definition and symptoms

The white spot disease, Ichthyo, is a parasitic disease. The parasite bores into the epidermis and gill epithelium of the host fish and causes a strong formation of mucus. White spots become visible on the fins and spread to the entire body of the fish within a short time. The fish rub against objects in the aquarium. The mucosa begins to peel off over a large area. As soon as the pathogen breaks through the skin, inflammatory changes form.

If the parasite reaches the gill area, the fish can hardly breathe due to the formation of mucus and the inflammation. Sometimes they swim directly under the surface of the water and try to gasp for air. The animals become tired, hide frequently and swim only slowly with fins attached to their bodies. The intake of food is greatly reduced, the fish emaciate.

Summary of the main symptoms

  • white spots on the fins and body
  • Mucous membrane detachment
  • Emaciation
  • Shortness of breath
  • altered swimming behaviour


The white spot disease is caused by a ciliate, Ichthyophthirius multifiliis. In its vegetative form, which can be up to 1 mm in size, the parasite settles in the skin of the fish and feeds on mucus and skin cells. As soon as the ciliate is sexually mature, it bores through the skin of the fish and sinks to the bottom of the aquarium. Cysts are formed at the bottom of the water, in which up to 1000 tomites (swarmers) with a size of 70 micrometers develop through multiple division.

As soon as the swarmers leave the cysts, new fish hosts are infected within 70 hours. This reproduction cycle takes between ten hours and six days, depending on the water temperature (4 – 28 degrees Celsius). At high water temperatures an explosive reproduction of the ciliates can take place.

What promotes the outbreak of spot disease?

  • New stocking
  • excessive water temperature
  • Stress
  • inferior feed


If white spot disease is not treated, it is fatal. If the fish survives the disease, it develops a premunity. It is infected with ciliates, but no longer falls ill itself. Fish newly put into the aquarium can be infected by the “carrier fish”.


The earlier a treatment starts, the higher the chances of reducing mortality in the fish stock.

1. Increase in water temperature

By increasing the aquarium temperature to 30 degrees Celsius the ciliates die. To prevent the fish from being affected by the high temperature, more oxygen must be introduced into the water by pumping and increased current.

2. Changing the water

By replacing 50% of the water, many of the ciliates are also removed from the aquarium.

3. Malachite green oxalate

The substance kills the gushers. Parasites that are directly on the fish are not affected.

4. Salt

By adding salt (without iodine) the pH value and conductivity of the water are changed.

5. Fish remedies

In the specialty market, various remedies against Ichthyo are offered. Many aquarists recommend in this context remedies of the company ESha

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