Causative agent: Lymphocystivirus — an iridovirus infecting fish cells
Lymphocystis is a viral disease caused by a member of the Iridoviridae family that produces distinctive cauliflower-like white or grey growths on the fins, skin, and occasionally the mouth of affected fish. Unlike many aquarium diseases, lymphocystis is rarely life-threatening on its own — most affected fish continue to eat and behave normally despite the disfiguring growths. In Australian aquariums, the disease is seen in both freshwater and marine setups, affecting a wide range of species including angelfish, bettas, platys, and marine tangs. Because it is caused by a virus, there is no effective medication, and treatment is largely supportive — maintaining excellent water quality, reducing stress, and providing a nutritious diet to support the fish's immune system. Many fish will gradually recover on their own over a period of months as the immune system mounts a response to the virus. However, lesions that block the mouth or gills may require veterinary intervention.
Symptoms
- •Wart-like white or grey cauliflower-shaped growths on fins, skin, or around the mouth
- •growths grow slowly over weeks or months
- •fish may otherwise appear and behave normally
Treatment
- •No antiviral cure
- •maintain pristine water quality
- •reduce stress
- •improve nutrition
- •large lesions blocking mouth or gills can be surgically removed by a vet
Australian Medications
- •No specific antiviral medication available in Australia
- •supportive care only
Commonly Affected Fish
- •All marine and freshwater fish
- •angelfish, bettas, gouramis, tangs, and platys are commonly affected
Important Notes
Self-limiting in many cases. Fish often recover naturally over months. Only dangerous if lesions block the mouth or gills.