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

The 63-day experiment was conducted to investigate the effect of different rice flour and molasses ratio on Pacific white shrimp, which were reared by biofloc technology. The five treatments (R10-M90, R30-M70, R50-M50, R30-M70, R10-M90) and one control 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, DO, and alkalinity are suitable for shrimp. The carbohydrate-supplemented treatments increased floc volume (FVI), mean floc length (MFL) and mean floc width (MFW), total suspended solids (TSS), reduced total ammonia nitrogen (TAN), nitrite (NO 2 - ), 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 final average weight, but final biomass and survival 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 had no negative impact on shrimp growth.