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.