Biofloc technology culture systems can increase the productivity of shrimp culture. Through the use of minimal or zero exchange, biofloc technology culture systems can also reduce the use of water. Diet enhancement through the addition of feed increases the amount of excreta. Together with unconsumed feed, the additional excreta increases the amount of suspended solids and reduces the concentration of dissolved oxygen. In addition, the excess of suspended solids can harm the culture by reducing light penetration. In turn, the lower light levels reduce the abundance of photosynthetic organisms (microalgae) that are also important for water quality and shrimp nutrition. The objective of this study was to evaluate the removal of suspended solids from the water of the culture system by a clarification process (i.e. particle settling). Two treatments were applied: with clarification and no clarification. Six tanks, each 35 m³, were used in the study. In the clarification treatment, 35 m³ of water with bioflocs was pumped from the experimental unit for 6 hours. The water passed through a settling tank (1,000 L) and was returned to the culture unit through gravity. The clarification treatment reduced total suspended solids (24.5%), turbidity (27%) and chlorophyll

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In a Biofloc Technology System (BFT), there is constant biofloc formation and suspended solids accumulation, leading to effects on water quality parameters that may affect the growth performance of cultured shrimp. This study aimed to analyse during biofloc formation the effect of different total suspended solids (TSS) levels on water quality and the growth performance of Litopenaeus vannamei shrimp in a BFT system. A 42-day trial was conducted with treatments of three ranges of TSS: 100-300 mg L À1 as low (TL), 300-600 as medium (TM) and 600-1000 as high (TH). The initial concentrations of 100 (TL), 300 (TM) and 600 mg L À1 (TH) were achieved by fertilization before starting the experiment. Litopenaeus vannamei juveniles with an average weight of 4.54 AE 1.19 g were stocked at a density of 372 shrimp m À3 . Physical and chemical water parameters and shrimp growth performance were analysed. After 6 weeks, TSS mean concentrations were 306.37, 532.43 and 745.2 mg L À1 for, respectively, TL, TM and TH treatments. Significant differences (P < 0.05) were observed in TSS, settleable solids, pH, alkalinity and nitrite, especially between the TL and TH treatments. Similarly, differences (P < 0.05) were observed in the growth performance parameters, specifically final weight, survival, feed conversion and productivity. The water quality parameters at lower range of total suspended solids concentration (TL) treatment resulted in a better performance of L. vannamei in the BFT system. The maintenance at range of 100-300 mg L À1 TSS is thus important to the success of shrimp culture.

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