Contralck is an effective drug for combating ichthyophthyriosis and other skin diseases of aquarium freshwater fish. With the correct dosage, they do not harm plants. Dosage of the preparation is 5 ml per 20 liters of water. In severe forms of the disease, the preparation is introduced into the aquarium at a rate of 10 ml per 20 liters of aquarium water. If after 5 days the symptoms of the disease have not passed, the treatment is repeated. Water filtration is not recommended during treatment, especially with activated carbon. Throughout the treatment, good water aeration must be established in the aquarium. After treatment, it is recommended to replace aquarium water and filter through activated carbon.