This work was carried out, firstly for investigating the different effects of various organic carbon sources [fructose (A), lactose (B), glucose (C)], and nitrogen sources [poultry manure extract (PM) and rumen liquor (RL)] which used at ratio 50:50% F/2 medium on maximizing production of biodiesel from the marine microalga Nannochloropsis oceanica. Secondly, we apply the residual lipid-free biomass as feed additives in Red tilapia aquaculture. In phase1, the biomass (DW), biodiesel contents and biochemical compositions of N. oceanica were determined. The results showed varied biomass and biochemical analysis in DW bases between treatments. However, A was achieved significantly the maximum DW for the algal biomass and protein percentage, whereas lipid accumulation was the most in RL as well as achieving the highest biodiesel content. In phase 2, algal biomass by-product (lipid-free) from the superior treatments A and RL were applied at 4 rates (1,2,3 and 4) for concentrations 25,50,75&100%, respectively that substituting soybean for feeding red tilapia larvae as compared with control CO. The initial weight and length of the larvae were 0.32g and 1.9 cm, respectively continued for a duration of 30 days of the experiment. After the end of the experimental period , growth performance, survival percentage (SR%) and biochemical analysis were estimated. The results revealed that SR% was higher significantly for RL2 than A1 (93% & 90%) as compared to control (86.7%). Accordingly, red tilapia carcass attained maximum protein contents for diets A1 & RL2 in whereas lipid content was maximum in control. Finally, authors suggesting the use of Roman liquor as a novel treatment for cost-effective promoting biodiesel content and the remained biomass with 50% substitution of soybean in the diet (RL2)achieved also good results for improving red tilapia aquaculture.