Net fish production and growth performance of Nile tilapia (Oreochromis niloticus) with an average weight 30 ± 0.65g were studied in earthen ponds offered graded dietary protein levels ( 25%, 35% and 45%) or natural food (control) for 170 days. Four treatments were applied in this study, each treatment was carried out in two ponds (100 × 40m) as replicates, each of one meter water column. The first three treatment were given a daily feeding rate 3% of fresh fish body weight and the fourth treatment did not receive any commercial feed but have only natural food produced from fertilizer ponds and served as control. The result showed that final body weight of tilapia averaged 230.21, 320.51, 330.30 and 115.65 g / fish fed T1, T2, T3 and the control one, respectively. Net production of tilapia averaged 1250.04, 1786.52, 1805.41, and 618.26 kg / pond in these fish culture treatments, respectively. Crude protein and fat of the whole body fish increased significantly (P< 0.05) with increasing dietary protein levels, while moisture and ash of the whole body fish decreased with increasing dietary protein levels. AST, ALT and muscles and plasma cholesterol increased with increasing dietary protein levels.  The results indicated that T3(45% protein) gave the highest growth and total production, whereasT2 (35%protein) gave the highest net return (11642.78L.E / ponds). This system T2 (35% protein) may be recommended for semi-intensive fish farming.