The motivation behind this study is to determine carefully the best supplemental level of spray dried Spirulina platensis as growth promoter for Nile tilapia (Oreochromis niloticus) and its effect on their performance, feed utilization, chemical body composition and gut health. Two successive experiments were conducted (Field and Lab scale). The Field – scale was conducted with a hapa-in-pond system with diets containing four levels of Spirulina platensis (0, 0.03, 0.05 and 0.07%) to determine the best level to supplement in tilapia diet. The Lab-scale experiment consisted of four treatments diets (Control one without any supplementation and three diets comparing between the best level of Spirulina obtained from the previous experiment and two standard commercial growth promoter with standard level of each one (Probiotic or prebiotic) ( 0.2% Biogen^®, 0.1 % Garlin Plus^® /kg diet ) respectively. Histological sections were collected to examine the gut health condition. The results of Field scale experiment showed that the dietary inclusion of 0.03 % Spirulina provided the best growth performance, feed utilization, and crude protein deposition than the other supplemented levels. On Lab scale side, spirulina at 0.03% conducted the same effect as commercial growth promoter (probiotic and prebiotic) in the same context, the intestine histological sections showed an increase of intestinal villi length in Nile tilapia. It could be concluded that Spirulina has a positive effect on gut conditions and that despite green water conditions contains natural cyanobacteria, the inclusion of 0.03 % of spray-dried Spirulina into tilapia diet positively affected growth performance and improve gut health.