Chylodonellosis of aquarium fish

Хилодонеллез рыб

Chylodonellosis is an invasive pathology in fish caused by the protozoan Chilodonella cyprini, which belongs to the infusoria. Curiously, but the causative agent of chilodonellosis feels comfortable at a temperature of aquarium water up to 10 degrees Celsius. It is for this reason, this pathology occurs in home aquariums is quite rare, especially if they do not fall below 20 degrees Celsius.

Aquarists should know that in case of gross violation of the rules of zoohygiene and at elevated values of the temperature regime, the pathogen can be in the aquarium indefinitely long time in the form of cysts, which are resistant to almost any aggressive environmental influences. Thus, the parasite remains viable, waiting for its time.

Chylodonellosis spread

Like most fish parasites, the chylodonellosis pathogen enters the aquarium with live food, plants or soil from open water. In this light, of particular importance is the need for prior disinfection of all objects placed in the aquarium. The same requirement applies to aquarium equipment.

The chylodonellosis pathogen parasitizes the gills of fish and skin epithelium. In the aquarium, which created favorable conditions for the life of fish, the fatal outcome of this pathology is practically not observed. However, if the fish have received for some reason wounds on the surface of the body, there is a high probability of secondary infection, which will significantly weaken the immune system and can lead the inhabitants of the aquarium to death.


The presence of chylodonellosis can be indicated by symptoms such as the fish’s fins clamped to the body and the constant need to rub against objects in the aquarium. Careful inspection can additionally reveal areas with abundant mucus secretion, which are located near the lateral line of the fish.

If the gills are affected, there is no mucus coating on the body. However, the fish still behaves restlessly and due to oxygen deprivation will almost constantly stay in the upper layers of the aquarium water, periodically swallowing atmospheric air.

Chylodonellosis treatment

Effective treatment of chylodonellosis is possible only in a quarantine aquarium, where a solution of malachite green is introduced. It may take 2 days to completely free the fish from the parasite.

If the pathology is detected in its neglected phase and there have already been cases of death of fish, treatment should be postponed. Otherwise, the weakened body of the inhabitants of the aquarium simply will not tolerate the use of high concentrations of drugs. Much more prudent will be to create in the general aquarium favorable conditions and wait until the fish begin to feel the need for food. Only then can treatment be started without fear of harming the fish.

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