54 SEPTEMBER 2017 • WORLD AQUACULTURE • WWW.WAS.ORG The need to produce more fish and shrimp requires a significant increase in aquatic production by about two-fold per decade in the near future. The UN Food and Aquaculture Organization stated that, within the coming decade, aquaculture production has to increase by 40 percent to meet current demand (FAO 2016). However, water and land limitations will not enable the achievement of this goal using conventional systems (Avnimelech et al. 2008). The aquaculture community has to move toward more intensive, highyielding systems, but such a transition cannot be done abruptly. There is a need for continual change through intermediate stages. This article describes a BFT-based farming system using vertical substrates as an alternative to suspended biofloc, as developed and practiced at a shrimp farm in India. Theoretical considerations and the mode of operation are briefly presented, followed by some results obtained by the farm. The purpose of this article is to introduce this modification of biofloc technology as an invitation to others to assess vertical substrate systems and to encourage further research and development of such systems. Biofloc technology (BFT) is based on the use of microbial consortia to metabolize organic residues in the pond, recycle nutrients and provide a healthy, integrated pond ecosystem. The use of BFT enables producers to significantly raise the intensity of shrimp and fish production in a way that does not demand very expensive and elaborate infrastructure. As such, it is commonly adopted and its use is increasing worldwide. Following development, successes and failures of BFT farms for shrimp and fish production, in general, big companies with sufficient trained personnel, infrastructure and financial support are doing well. The introduction of BFT to small family farms, mostly in less developed parts of the world, often fails. Biofloc technology is not very complicated, yet operators need to have some background and training in the biological mechanisms involved and the means to control the system. Regardless of the apparent simplicity of BFT, farmers, accustomed to managing extensive ponds (often for generations), have to pass through a significant mental transition to master management of intensive biofloc systems. Adapting Biofloc Technology for Use in Small-scale Ponds with Vertical Substrate Boriah Suryakumar and Yoram Avnimelech FIGURE 1. Scheme of organic particle sedimentation in a pond without (A) and with (B) vertical substrates. The introduction of vertical substrates provides an environment with high local concentrations of organic matter that enables development of microbial biomass. This community can be manipulated in the same way as that used in BFT, by manipulating the C/N ratio, and the attached biofilm provides similar services (ammonia control, natural food items) to those of a suspended biofloc community.
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