Frequent mortality was observed in the larval rearing facility of marine clownfish, A mphiprion sebae Bleeker. Mortality resulted in 80% loss of larval stock. Moribund larvae showed clinical signs typical of viral nervous necrosis, such as uncoordinated, corkscrew‐like swimming behaviour, hypersensitivity to stimuli, darkening of body and assembly into large groups, similar to bunches of grapes. The aetiology of the disease wa...