Biofloc technology – new blue revolution technique in intensive culture of tilapia

Introduction

Fish in a pond assimilate only 15–30% of the nitrogen added in the feed, remainder being lost to the system as ammonia and organic N in feces and feed residue. The organic N in feces and uneaten feed also undergoes decomposition and produces ammonia. Therefore, a high protein level in fish feed results in high concentration of ammonia in the water column which is detrimental to cultured animals. The most influential factor in aquaculture is feed cost and the most limiting factor is water/land supply. High stocking rates and aquatic animal rearing need wastewater treatment. Biofloc method is a wastewater solution that has acquired significance in aquaculture.

What is Biofloc technology?

Bioflocs are aggregates (flocs) of algae, bacteria, protozoans and other kinds of particulate organic matter such as feces and uneaten feed. Each floc is held together in a loose matrix of mucus that is secreted by bacteria. The bacterial cells are made up of proteins and they have to maintain a fixed carbon/nitrogen (C/N) ratio in their cell. Biofloc technology (BFT) is a technique of enhancing water quality through the addition of extra carbon to the aquaculture system, through an external carbon source or elevated carbon content of the feed. BFT is considered the new “blue revolution” since nutrients can be continuously recycled and reused in the culture medium, besides the benefit of minimum or zero-water exchange.

Biofloc technology was introduced by Dr. Yoram Avnimelech in Israel. The main concept is that producers could piggyback off the nitrogen cycle and let beneficial bacterial colonies proliferate in culture water. The biofloc system was developed under the same principle that regular waste water treatment plants have, in which the microbes grow from feces of the cultured organisms being, transforming it into less complex organic products that can be consumed. Common practices in BFT systems consist of indoor tank BFT culture of Nile tilapia; outdoor culture of tilapia in BFT tanks; the raceway system with biofloc for L. vannamei broodstock family selection; the Penaeus monodon culture in BFT ponds; and the L. vannamei culture in BFT tanks. The biofloc fish farming materials system was developed to improve environmental control over the development of aquatic animals.