Effect of the addition ratio of rice flour and molasses on the biomass of Pacific white shrimp (Litopenaeus vannamei) stocked by biofloc technology

The 63-days experiment was conducted to investigate the effect of different rice flour and molasses ratio on Pacific white shrimp, which were reared by the biofloc technology. The six treatments (control, R10-M90, R30-M70, R50-M50, R30-M70, and R10-M90) were randomly arranged with three repetitions in 18 plastic tanks. The content of adding two carbohydrate sources was calculated and added to water to gain the C:N ratio of 15:1. The experimental shrimps (mean initial weight of 0.095 g) were stocked at a density of 150 m − 3 and fed Lotus pellets (40% protein) for 63 days. The results showed that the temperature, pH, alkalinity and dissolved oxygen (DO) are suitable for shrimp and slightly fluctuate. The carbohydrate-supplemented treatments increased chemical oxygen demand (COD), biofloc volume (BFV), biofloc size, total suspended solids (TSS), volatile suspended solids (VSS), reduced total ammonia nitrogen (TAN), nitrite, P-PO 4 as compared to control, in which R70-M30 treatment exhibited the most pronounced effects. Shrimp culture applying biofloc process stimulated the density of total bacteria and zooplankton to thrive and limited phytoplankton. Maintaining the C:N as 15 by adding carbohydrates showed a more effective impact. There was no significant difference in the mean weight of shrimp growth parameters, but biomass and yield tended to be highest in treatment R70-M30 (results were only significantly different from R90-M10). In conclusion, combining two carbohydrate sources positively improved water quality and provided shrimp feed. The ratio of 70% rice flour and 30% molasses was suggested following the conditions of this study.