The C/N ratio for the anoxic period was approximately 0.1 g of TOC/g of nitrate nitrogen. For the aerobic system, the percent survival of shrimp under control and treatment group experiments was 34% and 54%, respectively while for the recirculation system, the percent survival was decreased to 26% and 49% for control and treatment group, respectively. This finding showed that the recirculation of water after the aerobic and anoxic systems slightly affected the shrimp survival but the shrimp were significantly affected for control group (p