An experiment was conducted to determine for the optimal phosphorus supplemention to carp feed which contains $50\%$ soybean meal, with $32\%$ protein content to obtain maximum growth of the Israeli strain of common carp (Cyprinus carpio). The experimental fish were between 100 g and 1000 g in body weight. The results, obtained were as follows: the optimum amount of phosphorus added to the experimental feed was $1.6\%$ as $NaH_2PO_4{cdot}2H_2O$ which brings up the total amount of available phosophorus to $0.504\%$ of the feed. This amount is slightly less than the amount, $0.6-0.7\%$ which was previously reported for the Japanese native strain of carp which weighted around 4.5g. Thus there seems to be some difference for the requirement of phosphorus between the sizes of carp.