Biofloc system is the environment friendly blue revelation technology which enhanced productivity, ensure animal healthcare and bio-security and conserved water while optimum biofloc volume is a paramount important for productivity and survival of animal culture. The study was conducted to optimize the suitable floc volume for Macrobrachium rosenbergii post larve (PL) culture. The experiment was conducted in five different biofloc volumes i.e. floc volume 2-5 ml (BF2-5), 7-10 ml (BF7-10), 12-15 ml (BF12-15) and zero-exchanged biofloc (BF-Z) with triplicates during one month period. Giant prawn post larvae stocked at the rate of 5 individuals L-1 (5000 PL m-3) with an average initial weight ± SD of 21.83 ± 12.92 mg in 12 polyethylene tanks (100 L).
The highest survival (82.33%) was found in 2-5 ml biofloc volume and followed by 72.33%, 62.0% and 14.66% in 7-10 ml, 12-15 ml and zero-exchanged biofloc volume, respectively. The minimum FCR (2.12) was recorded in 2-5 ml floc volume while the maximum FCR (12.11) was found in zero-exchanged biofloc (Table 1). It is revealed that the density of Vibrio spp. was also the lowest in 2-5 ml volume and it was the highest in zero-exchanged biofloc. Thus, it might be suggested that 2-5 ml biofloc volume could be apply for commercial venture of M. rosenbergii post larvae nursery phase.