Strategies for water preparation in a biofloc system: Effects of carbon source and fertilization dose on water quality and shrimp performance

This study aimed to evaluate the effect of different carbon sources, at two fertilization doses, on water quality and shrimp performance in a biofloc system. To accomplish this, marine shrimp Litopenaeus vannamei post-larvae (PL17) were cultured in intensive (150 animals m−2) zero water-exchange biofloc technology (BFT). The experiment was conducted during 39 days, and 12 tanks (0.85 m3) were used. Treatments consisted of two sources of organic carbon, rice bran (RB) or molasses (MO); each supplied at two rates (25 mg L−1 and 100 mg L−1 of total suspended solids). At the end of the fertilization period, water column respiration rate was higher, but net ecosystem production was lower in RB100 and MO100 treatments. These results indicated that the different carbon sources evoked similar metabolic behavior among microbial communities. Ammonia level was significantly higher in the MO100 treatment after the preparation period (7 days). No significant differences were observed in water quality parameters between treatments at the end of the experiment, except for orthophosphate. RB yield was 22% higher and the feed conversion rate 15% lower compared to MO. Therefore, RB could be used as a carbon source for biofloc systems, increasing shrimp yield, while decreasing feed conversion rate.