This study was conducted to investigate the effect of partial and complete replacing artificial fish feed with Azolla in feeding Nile tilapia fish. Five treatments were done and fish were distributed randomly, where the only variable was the percentage of Azolla addition by using ten mesh cages of 0.5 m³ (75*80*80 cm) of brackish water. Artificial feed was replaced by Azolla as 0%, 25% , 50% ,75% and 100%, in the treatments T₁, T₂, T₃, T₄ and T₅, respectively. The experiment lasted 135 days, and water measurements were taken from salinity, acidity, oxygen and ammonia. The weight of the fish was taken every 15 days, and analyzes were made for data on growth, nutritional transformation, weight, length and feed consumption for fish. The results showed that the mean final weight of individuals decreased significantly (P<0.05) in the experimental treatments with increasing Azolla as a supplementary feed. The best treatments were T2, which is the substitution of Azolla by 25%, and there is no difference between it and the treatment T1, which is the control. Therefore, it is recommend to use of Azolla as an inexpensive alternative in feeding fish at a rate of 25% to give the best desired results in terms of length and weight.