# Biofloc Technology for Nile Tilapia Fry: Technical and Economic Feasibility, Solids Control, and Stocking Density

## TL;DR

This study shows that biofloc technology can sustainably raise Nile tilapia fry by improving water quality and reducing feed costs.

## Contribution

The study demonstrates the technical and economic viability of biofloc technology for Nile tilapia fry production at a pilot scale.

## Key findings

- TSS levels between 200 and 600 mg·L−1 improved water quality and fry performance.
- Higher stocking densities reduced survival and final weight while increasing nitrogenous compounds.
- BFT achieved survival rates above 85% and net margins of 18.5 to 41.9% in pilot cycles.

## Abstract

Aquaculture is one of the fastest growing food production sectors, but its success depends on developing methods that reduce costs and environmental impacts. This study evaluated the use of the biofloc system, a technique that uses microorganisms and organic matter present in the water to improve water quality and provide natural food for fish. We tested whether this system could support the early growth of Nile tilapia fry under different stocking densities, and whether controlling the amount of solids in the water would improve results. Our findings showed that the biofloc system can partially replace feed, maintain water quality, and support the growth of tilapia fry. These results demonstrate that the system is technically feasible and may reduce production costs in aquaculture.

This study evaluated the technical and economic feasibility of the biofloc technology (BFT) system during the fry rearing phase of Nile tilapia (Oreochromis niloticus), focusing on suspended solids management, stocking density, and economic performance at a pilot scale. Three trials were conducted. The first assessed the effects of four total suspended solids (TSS) ranges (0–200, 200–400, 400–600, and 600–800 mg·L−1) on larval performance and water quality. TSS levels between 200 and 600 mg·L−1 promoted improved water quality and zootechnical performance. The second trial tested five stocking densities (2, 4, 6, 8, and 10 larvae·L−1), evaluating their impact on water quality, survival, and size uniformity. Higher densities negatively affected survival (R2 = 0.84) and final weight (R2 = 0.92), while also increasing solids and nitrogenous compounds, thus impairing performance (p < 0.05). The third trial monitored six production cycles at pilot scale, evaluating zootechnical parameters, sex reversal efficiency, and economic indicators. All cycles showed survival rates above 85%, sex reversal close to 100%, and positive net margins (18.5 to 41.9%), demonstrating the viability of BFT for commercial fry operations. The results emphasize the importance of controlling suspended solids and stocking density to maintain water quality and optimize larval performance. Furthermore, the system proved economically viable, with good feed conversion rates and profitability, even without water exchange. These findings support BFT as a sustainable and efficient alternative for tilapia fry production, offering significant water savings and promising economic returns when properly managed.