Vitamin C requirement of the Mexican native cichlid Cichlasoma urophthalmus (Gunther).
The dietary vitamin C requirement was estimated for Cichlasoma urophthalmus, a particularly important Mexican native cichlid. Fry with initial weight of 160 to 170 mg were fed for 90 days on diets containing 10 different amounts of vitamin C ranging from 0 to 10 240 mg/kg diet. Fish fed on the diet without vitamin C showed high mortality and significantly reduced growth compared with the other treatments. Fish fed on diets containing vitamin C 0, 40 and 78 mg/kg showed an external pathological appearance which was not observed with fish fed on diets containing higher amounts of vitamin C. The external signs of deficiency observed were dark colouration, short operculae, haemorrhages in the eyes, head and fins, erosion of the skin and fins, loss of scales, exophthalmia, swollen abdomen, iritis, scoliosis and changes in the head bones. The minimum level of vitamin C required for normal growth was 40 mg/kg diet, and the minimum amount required to ensure healthy fish was 110 mg/kg.