Optimizing Stocking Density for Enhanced Tilapia and Lettuce Production in NFT Aquaponics

Water is an essential resource in arid regions; therefore, its management and use must be rational. Aquaponics, which integrates aquaculture and hydroponics, represents an innovative approach to efficient water use, particularly in arid environments. The objective of this study was to determine the effect of fish stocking density on the growth performance of lettuce (Lactuca sativa) and Nile tilapia (Oreochromis niloticus) in a nutrient film technique (NFT)-based aquaponic system under arid conditions. A randomized block design was adopted with three fish stocking densities (1.5, 3.0, and 4.5 kg m-³), expressed as Nile tilapia biomass per unit volume of water. Water temperature remained within the optimal range across all treatments and did not differ significantly among them. However, pH and dissolved oxygen (DO) concentrations were significantly influenced by stocking density, with DO concentrations decreasing as stocking density increased. Higher stocking densities also resulted in increased nitrate, nitrite, and total ammonia nitrogen concentrations, whereas potassium and soluble reactive phosphorus concentrations remained stable. Tilapia reared at the lowest stocking density (1.5 kg m-³) attained significantly greater final weight, weight gain, and specific growth rate, whereas survival rates did not differ significantly among treatments. In contrast, lettuce grown at the highest fish stocking density (4.5 kg m-³) had significantly greater biomass, head weight, and leaf and root lengths, possibly due to greater nutrient availability. These findings highlight the need to balance fish and plant production objectives to optimize the efficiency of NFT-based aquaponic systems.