An experiment on the phosphorus requirement and the proper Ca/P ratio in the diet of the black sea bream using the phosphorus gradient method (with casein as basic diet, sodium dihydrogen phosphate as source of phosphorus, and calcium lactate as source of calcium) showed that growth was greatly affected by the diet’s phosphorus content and Ca/P ratio. Inadequate phosphorus in the diet resulted in slow growth and poor food conversion ratio (FCR). Analyses of the fish body showed it contained a high level of lipid but a low level of moisture, ash, calcium and phosphorus. The optimal values of phosphorus and Ca/P ratio in the black sea bream diet are 0.68% and 1:2 respectively. Phosphorus in excess of this optimum value resulted in slow growth or even death. The results of this experiment clearly indicated that phosphorus is the principal mineral additive affecting black sea bream growth. An experiment on the phosphorus requirement and the proper Ca / P ratio in the diet of the black sea bream using the phosphorus gradient method (with casein as basic diet, sodium dihydrogen phosphate as source of phosphorus, and calcium lactate as source of calcium) showed that growth was greatly affected by the diet’s phosphorus content and Ca / P ratio. Inadequate phosphorus in the diet resulted in slow growth and poor food conversion ratio (FCR). Analyses of the fish body showed it contained a high level of lipid but a low The optimal values ​​of phosphorus and Ca / P ratio in the black sea bream diet are 0.68% and 1: 2 respectively. Phosphorus in excess of this optimum value resulted in slow growth or even death. The results of this experiment clearly indicated that phosphorus is the principal mineral additive affecting black sea bream growth.