Enhancing brackish water tilapia seed production with biofloc technology

Abstract

Aim of this study was to observe the effect of biofloc technology application to enhance brackish water tilapia production. This research was conducted by using two different stocking densities at 3000 seeds.m-3 (D-3000) and 6000 seeds.m-3 (D-6000). It was performed on concrete tanks of 5.5 x 1.8 x 0.8 m in dimension (active volume 5 m3) located under semi-indoor building. Biofloc formation were stimulated by adding molasses as carbon source by adjusting C:N ratio to around 10:1. The water salinity increased gradually after 8th day and reached up to 15 ppt during harvest. The result showed that brackish water tilapia seed survival rate of D-3000 and D-6000 was in range 77-79 %, biomass were 0.60 - 0.85 kg.m−3, and seed uniformity was 77-82%. Biofloc or floc volume of D-3000 was higher than D-6000 at 10 ml.l−1 and 3 ml.l−1 respectively. At the beginning, microalgae population was dominated by Bacillariophyceae while Chlorophyceae dominated at the end of rearing periods, and Rotifer density around 64-191 ind.ml−1. Total bacteria observed was in range of 3x103-14x104 cfu.ml−1. For both treatment nitrite (N-NO2) was 0.000-0.029 ppm, nitrate (N-NO3) was 0.000-0.445 ppm or less than 0.5 ppm, dissolved oxygen (DO) range was in optimal conditions (5.8-6.2 ppm) for tilapia rearing.