The present study was conducted over 96 days in order to compare between the effects of floating and sinking diets with different levels of a probiotic on growth performance, food utilization and chemical composition with all-male mono-sex juvenile Nile tilapia (Oreochromis niloticus). The treatments were two floating and sinking diets supplemented with three levels of the probiotic PRO-LYNE^®, being 0%, 1% and 2% of the diets. Each hapa (measuring 2 × 3 × 1 m³) was suspended in an earthen pond (4000 m²). There were 6 treatments, each consisting of 2 replicates, stocked with fish of average initial body weigh 60 g. A total of 366 fish were randomly distributed into 6 experimental groups. The stocking density was 5 fish / m³ for all the hapas. Fingerlings were fed a commercial diet containing 25.2% crude protein and at feeding rates of 4% of their fresh biomass in each hapa for the first 1.5 month and 3% until the end of the experiment. The results of the present study revealed that performance and production and economic efficiency of Nile tilapia reared in net hapas in earthen ponds significantly increased, when they were fed the floating pellets supplemented with probiotic at level 1%.