Twenty-five blind, adult clownfish (Amphipiron oscellaris) from Instant Ocean Hatcheries, Inc. were examined histopathologically during a two-year period. The only consistent lesion associated with the blindness was the presence of crystals in the kidney tubules. Crystals resulted in tubular necrosis and eventual kidney destruction.

Kidney tissue was digested in sodium hydroxide to obtain the crystalline material. The crystals were identified by X-ray diffraction and electron microprobe analysis as calcium oxalate monohydrate.

The histopathology of the oxalosis and blindness are discussed. Possible nutritional causes and attempts to reproduce the disorder through diet are also presented.