Phosphorus and calcium requirements in the diet of the American cichlid Cichlasoma uraphthalmus (Gunther)

An experiment was carried out with Cichlasoma urophthalmus (Gunther) juveni les to determine the phosphorus requirement and its interaction with dietar y calcium. Twelve isoenergetic and isoproteic diets were prepared using a b asal artificial diet containing vitamin-free casein, dextrin, starch, corn oil, fish oil, vitamin mixture and a mineral mixture free of calcium and ph osphorus. Calcium and phosphorus levels were determined in the casein. To t he basal diets were added different concentrations of phosphorus as potassi um monophosphate (0.5, 1.0, 1.5 and 2.5 g kg(-1)) and calcium as calcium ca rbonate (0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0 g kg(-1)). These concen trations resulted in varying Ca-P ratios (1:1, 1.33:1, 1.5:1, 1.6:1 and 2.0 :1). Calcium and phosphorus concentrations in the watts were 84 mg kg(-1) a nd 0.003 mg kg(-1), respectively. The diet with 0.5 g kg(-1) phosphorus res ulted in deficiency signs such as reduced growth, high conversion ratio, hi gh Fat content and low bone mineralization. Increased levels of dietary cal cium and phosphorus both gave improved growth and mineralization. Mineraliz ation continued to increase with dietary phosphorus levels above that requi red for maximum growth. The optimum level of phosphorus in the diet was 1.5 g kg(-1), the optimum calcium level was 1.8 g kg(-1) and the optimum Ca-P ratio was 1.3. Carcass lipid levels were inversely related to dietary phosp horus.