Sustainable, efficient alternatives to pond culture technology for finfish

The South Asia Fisheries Research Project (SAFRP) finfish production program was designed to explore the cost-effective production of fish in a land-based facility using advanced technology. The project was designed to
1. Maximize land and water use and use local materials and personnel to reduce costs and.
2. Simplify operating requirements to reduce training costs and enhance predictability and stability
of outcomes over time.

The technology of choice was Biofloc that can be loosely defined as managing two different crops simultaneously in the same tank, fish and plankton. Biofloc Technology (BFT) eliminates the need for separate systems for nitrification, growout and degassing reducing the infrastructure complexity compared to Recirculating Aquaculture Systems (RAS) and their inherent cost.

Methodology: BFT requires extensive mixing and aeration of the water to facilitate adequate oxygen levels and nitrification of fish waste products. The current SAFRP design requires tanks in order to optimize this water movement and eliminate issues normally related with pond sediment.

A group of 50-m³ tanks were stocked with sex reversed tilapia to evaluate land-based finfish production using biofloc technology. The tanks used aeration nozzles to simultaneously mix and aerate the water. The nozzles also facilitate efficient self-cleaning and concentration of waste products in conjunction with a dual drain tank configuration.

Nitrification was accomplished using bioflocs in the water maintaining acceptable ammonia and nitrite levels throughout the growout period. The nitrate levels and Total Suspended Solids (TSS) were controlled through limited water exchange and solids removal. The tank design includes an additional 3m³ sediment tank that receives 15% of the water flow from the main tank center drain. The waste produced is processed
and composted and used as soil amendments.

BFT requires maintaining an adequate carbon/nitrogen (C/N) ratio in the water to efficiently grow bioflocs. This normally requires additional carbon, like rice flour or molasses, to be added in addition to fish feed. The C/N ratio, size and age of the bioflocs is controlled by managing the waste flow and carbon additions.

Results: After ten years of research and development, the SAFRP tanks are uniquely designed to efficiently facilitate waste removal and minimize water losses while mixing and aerating the water. This includes the development of a patent-pending nozzle which reduces energy production costs significantly.

A pond is usually limited to about 5000kg/ha, whereas the current operation of 60 tanks produces 10 times as much product in the same space and allows mixing of age and species cohorts during the production cycle. The larger tank base also allows the evaluation of a production scale BFT facility with a range of operational issues related to specie variation, production logistics, bio security, and water quality.

Annually, the SAFRP tanks produce 230,000 kg of fish. Fish quality has been significantly enhanced with reduction of oL-flavors, and FCR has been decreased by 10-20% through the biofloc technology. Additionally, the SAFRP hatchery produces 100 million? fingerlings each year that supply both SAFRP’s own grow out tanks and are sold to local fishermen for pond and other uses.

Audience Take Away Notes: 
• How to implement Biofloc in a difficult environment
• Biofloc cultivation
• Infrastructure build/maintain
• Applying a unique design to finfish production
• Nozzles
• Twin drains
• Tank advantages
• Bio security
• Production logistics
• Water management – Mature water/immature water/water exchange