Plant protein ingredients are utilized for fish feed, but they contain phytate. The thermostable phytase-added diet will have no cost for preservation. Therefore, it will be deployed to resolve the problems of the phytate. This study aimed to assess the effect of phytase additives on growth indices, digestibility and utilization, carcass composition, and sustainability of African Catfish fed a combination of diets. Five diets were formulated Phytase (Ronozyme hiphos GT) (500; 1000, 1500, 2000, 2500) FYT.kg-1 diet and a control 0 FYT.kg-1 diet. Comprise of 18 tanks (200 liters each), stocked with 20 fish of mean weight 20.98 ± 0.01 g, and fish were manually fed thrice for 84 days. Fish showed a significant (p < 0.05) inclusion level-base improvement of mean final weight from 81.60 ± 1.49 g in 0 FYT.kg-1 to 113.19 ± 3.18 g in 2000 FYT.kg-1, and feed conversion ratio from (2.11 ± 0.06 to 1.56 ± 0.06), protein digestibility from (93.43 ± 0.03 to 98.19 ± 0.03) %, and carcass crude protein from (36.11 ± 0.11 to 44.03 ± 0.06) % in 0 FYT.kg-1 and 2000 FYT.kg-1 respectively. Intestine villi height improved from (405.49 ± 0.49 to 611.03 ± 0.98) µm in (0 to 2000) FYT.kg-1. The net profit increased from (954.18 ± 53.64 to 1995.42 ± 114.48) in (0 to 2000) FYT.kg-1. The 2000 FYT.kg-1 inclusion level reflected the best growth, digestibility, carcass composition, and sustainability in African catfish, while the optimal inclusion level was 800 FYT.kg-1 diet.