Biofloc management with different flow rates for solids removal in the Litopenaeus vannamei BFT culture system

Different water flows for solids removal in the Litopenaeus vannamei BFT system were evaluated. One control (no solids removal) and two treatments using different water flows, high (3945 L h(-1)-HF) and low (1750 L h(-1)-LF), were used with no water replenishment after each process, and the total dry weight of the solids was measured. L. vannamei (0.18 +/- 0.06 g; 350 individuals m(-2)) were stocked in 35-m(-3) tanks. For 17 weeks, the physical and chemical parameters were maintained within the recommended. To keep the total suspended solids concentrations at approximately 500-600 mg L-1, clarifying was performed. The average water volume flowed by clarifiers was significantly different (p < 0.05) between HF (205 +/- 34 m(3)) and LF (114 +/- 24 m(3)). There was a significant decrease (p < 0.05) in the final tank volume in HF (28.09 +/- 0.92 m(3)) and LF (28.62 +/- 1.38 m(3)) due to the clarifying. Before clarifying (initial sample) and at the end of experiment (final sample) were not significantly different (p > 0.05) for crude protein, moisture or ash. The crude lipid of the LF in the final period was significantly lower (p < 0.05) compared to others in both periods. The survival, productivity and food conversion ratio were significantly better (p < 0.05) in the HF and LF treatments compared to those of the control. The best shrimp performance was obtained with solids removal. The lower flow in the clarifier facilitated particle settling, allowing adjustment of the flow.