Abstract
Developing more efficient and potentially sustainable nutrient supplementation strategies, such as organic amino acids and biostimulants, is critical for advancing aquaponics and reducing reliance on synthetic inputs. This study evaluates the synergy of fish amino acid (FAA) - an organic nitrogen source that enhances nutrient availability and a seaweed-based biostimulant (SB) - rich in bioactive compounds that stimulate plant growth, in a coupled nutrient film technique (NFT)-based aquaponics system to enhance Nile tilapia (Oreochromis niloticus) growth and Brahmi (Bacopa monnieri) biomass. The research aimed to quantify the interaction effects of these SB and FAA on key performance indicators for both fish and plants, thereby identifying an optimal organic fertilization strategy.
To test this, four treatments combining different concentrations of SB and FAA were applied in triplicate for 6 weeks, alongside a no-input control. The treatments included supplementation with 25% SB and 2.5 mL/L FAA (SB25–FAA2.5), 25%SB and 5.0 mL/L FAA (SB25–FAA5.0), 45% SB and 2.5 mL/L FAA (SB45–FAA2.5), and 45% SB and 5.0 mL/L FAA (SB45–FAA5.0). These organic fertilizers were applied at 4-day intervals by foliar spray to the plants in the evening . Fish metrics (weight gain, specific growth rate, and feed conversion ratio ) and plant metrics (height, shoot number, and fresh biomass) were monitored fortnightly. W ater physicochemical parameters (nitrogen dynamics, pH, dissolved oxygen, total dissolved solids, electrical conductivity, alkalinity) were monitored once a week. The results demonstrated significant concentration-dependent responses to combined FAA-SB treatments, with SB45–FAA2.5 achieving optimal performance efficiency compared to the other treatments . As shown in Table 1, SB45–FAA2.5 exhibited the highest plant growth rate and fresh biomass accumulation . While SB45–FAA5 produced the highest absolute biomass, SB45–FAA2.5 demonstrated superior resource utilization, achieving 87.3% of SB45–FAA5.0 ’s yield with 50% less FAA input. SB45–FAA2.5 also shown to be the most suitable for tilapia growth, with the higher weight gain and feed utilization in this treatment . These results validate the synergistic potential of FAA-SB combinations for commercial aquaponics applications.