Giant prawn Macrobrachium rosenbergii is a high demand aquaculture commodity globally and culture in many Asian countries. Biofloc aquaculture system provides food, nutrition and robustness to culture animal where appropriate carbon source and carbon nitrogen (CN) ratio are prerequisite for removal of hazardous nitrogenous compound from culture environments. Five different carbon sources viz. wheat bran (WB), rice flour (RF), molasses (MO), maize starch (MS) and palm kernel expeller (PKE) and four different carbon nitrogen ratios of 10 (CN10), 15 (CN15), 20 (CN20), 25 (CN25) and control (without carbon source) were examined under five treatments with triplicates of two separate experiments to get the suitable carbon source and CN ratio for M. rosenbergii post larvae. A total of 15 tanks (125 L each) were used for evaluating the water quality conditions, microorganisms and giant prawn PL growth performance and proximate composition of prawn and biofloc.
The highest survival (88.67%) and lowest FCR (2.21) was found using maize starch carbon source (Table1). MS biofloc contained (1.97%) higher (p< 0.05) crude lipid which also led higher lipid (4.02%) level in prawn carcass. Higher final weight (116.34 mg) and lower FCR (2.44) was observed in CN ratio 20 based biofloc system. CN ratio 20 biofloc was showed significantly (p< 0.05) higher crude protein (29.57%) which also led to higher (p< 0.05) protein (65.85%) in prawn carcass. Higher rotifers were observed in CN ratio 20 based biofloc system (Table 2). Thus, we recommend maize starch carbon source and CN ratio 20 for prawn nursery operation in biofloc system which would be applied in commercial venture to enhance productivity.