Effect of Stocking Density on Growth Performance of Tilapia (Oreochromis Niloticus) and Lettuce (Lactuca Sativa) in A NFT Aquaponic System Under Arid Region Conditions

Abstract

Aquaponics is a sustainable food production method that combines aquaculture and hydroponics, minimizing resource demand and environmental impact. This method is still in its early stages of adoption in Algeria, and its operations and basic principles are still largely unexplored to various fish and vegetable species. This study aimed to identify the influence of fish stocking density on water quality and growth performance of the Nile Tilapia (Oreochromis niloticus) and Lettuce (Lactuca sativa) in an NFT aquaponic system under arid region conditions. Three fish stocking densities were established: 1.5 kg/m³, 3 kg/m³, and 4.5 kg/m³, each with three replicates. For each stocking density, we measured plant growth performance as well as fish growth. Furthermore, water quality parameters in both the fish and the vegetable tanks were monitored. The results showed that the production of lettuce significantly varied and increased with increasing stocking density as, 196.91±2.66, 205.14±12.27 and 250.74 ± 17.7 g for 1.5, 3 and 4.5 kg/m³, respectively.  However, the final weight of Tilapia decreased when stocking density increased and was 55.97 ± 1.66, 34±1.98 and 27.35±1.97g for 1.5, 3 and 4.5 kg/m³, respectively. The pH was approximated to be neutral and fluctuated between 6.78 ±0.04 to 7.78 ±0.02. With increased stocking density, the dissolved oxygen declined and ranged from 3.39±0.49 to 5.56±1.27 mg/L in the fish tanks. The ranges of nutrient accumulation across the different stocking densities of Tilapia were: 0.033±0.004 - 0.038±0.003 mg/ L for total ammonium nitrate (TAN); 1.13±0.032-1.38±0.022 mg /L for nitrate and 0.01±0.001- 0.07±0.062 mg/ L for nitrite. Overall, the results showed that the medium stocking density of 3 kg/m³, which provided the best performance for the tested aquaponics system, is highly recommended.