The objective of this study was to evaluate the effect of the addition of Navicula sp. on the growth and fatty acids profile of Litopenaeus vannamei postlarvae in a biofloc system (BFT). Four treatments were used: BFT; BFT 2.5N (addition of 2.5 × 10⁴ cells/ml of Navicula sp.); BFT 5N (addition of 5 × 10⁴ cells/ml of Navicula sp.) and BFT 10N (addition of 10 × 10⁴ cells/ml of Navicula sp.), all in triplicate. The shrimp (1 ± 0.01 mg) were stocked at a density of 3,000 postlarvae/m³ and fed with commercial feed. The diatom was added every 10 days, and at the end of 42 days, shrimp performance, water quality and proximal composition were evaluated. The BFT 5N and BFT 10N treatments had higher performance values, highlighting the values of productivity (2.30 and 2.42 kg/m³) and specific growth rate (15.92 and 16.08%/day), which were higher than the other treatments. In addition, the highest levels of fatty acids were observed in treatments with diatom (BFT 5N and BFT 10N), indicating the benefits of Navicula sp. on growth enhancement and fatty acid content of L. vannamei postlarvae grown in biofloc systems.

A 42-day trial was conducted to evaluate the effects of a low-salinity biofloc system with different stocking densities on water quality and zootechnical performance of Nile tilapia fingerlings (10 g/L). Four treatments were tested at different densities: 500 fish/m³, 750 fish/m³, 1,000 fish/m³ and 1,250 fish/m³, all in triplicate. Fingerlings of Oreochromis niloticus (initial mean weight of 1.17 ± 0.05 g) were stocked in twelve experimental black-plastic tanks (40 L) with no water exchange during the experimental period. Molasses was added daily to the system at 30% of the amount of feed, and fish were given four daily rations of a formulated feed composed of 36% crude protein and 9% lipids. Water quality variables (dissolved oxygen, pH, salinity, TAN, NO2, NO3 and PO43) did not demonstrate significant differences between the treatments. However, significant influences (α ≤ 0.05) of the stocking densities were observed for total suspended solids, settleable solids, final weight, yield, and protein efficiency ratio. The results showed survival over 96%, final weight values between 12 and 18 g, yield between 9.49 and 15.27 kg/m3, water consumption of 52 to 101 L/kg fish, and total time of settling chambers between 238 and 305 h/kg fish. These results indicate a negative effect of stocking density on final weight, survival, alkalinity, NO2, PO43 and water consumption, and a positive effect on yield in Nile tilapia fingerling culture (1-20 g) in a low-salinity biofloc system with densities up to 1000 fish/m³.

The aim of this study was to evaluate the effect of supplementation with Chlorella vulgaris and molasses application rates on water quality, zootechnical performance, proximate composition and health status of Nile tilapia (Oreochromis niloticus) fingerlings cultivated in low-salinity (10 g L-1) biofloc systems. Four treatments were tested in a factorial design (supplemented with microalgae and molasses application rates): BFT-C30 (Biofloc supplemented with C. vulgaris and molasses application rates of 30% of the total daily feed); BFT-30 (Biofloc with molasses application rates of 30% of the total daily feed); BFT-C50 (Biofloc supplemented with C. vulgaris and molasses application rates of 50% of the total daily feed) and BFT-50 (Biofloc with molasses application rates of 50% of the total daily feed), for 70 days. Fingerlings of O. niloticus (initial mean weight of 3.15 ± 0.5 g) were stocked at a density of 680 fish m-3 in experimental units (50L), where 50% of this volume was biofloc previously matured. Throughout the experiment, they were supplemented with C. vulgaris every five days at the concentration of 5x104 cells mL-1. A significant interaction between supplementation with C. vulgaris and molasses application rates for final weight and length, survival, feed conversion ratio, specific growth rate, water consumption, protein efficiency ratio, sedimentation time, planktonic community and hematological indices were observed. The results indicated that the high molasses application rates (50%) in the biofloc system affects the zootechnical performance, water consumption, sedimentation time and the hematological indices of the Nile Tilapia fingerlings, hampering their development. Therefore, molasses application rates of 30% of the total daily feed for the tilapia fingerlings culture in low-salinity biofloc system is recommended.

Na presente pesquisa avaliou-se o efeito da relação carbono/nitrogênio (C:N) na qualidade da água, produtividade e composição centesimal dos alevinos de Oreochromis niloticus durante 58 dias de cultivo. O desenho experimental consistiu em quatro tratamentos: um sistema convencional (controle) e três sistemas de biofloco (CN10, CN15 e CN20). Foram utilizadas 12 unidades experimentais de 0,04 m3 com 30 peixes (750 peixes m-3) com peso médio individual de 1,55 ± 0,01 g. Verificou-se a existência de interação entre os parí­¢metros de qualidade da água do sistema de biofloco e os parí­¢metros produtivos dos alevinos de tilápia. O tratamento CN10 apresentou baixa produção de sólidos sedimentáveis, 38,61 ± 0,54 mL L-1 (p<0,05), fato esse que contribuiu para o rápido crescimento dos indiví­­duos (21,7 ± 2,18 g), atingindo produtividade final média de 15,50 ± 0,81 kg m-3 (p<0,05). É possí­­vel concluir que o cultivo de alevinos de O. niloticus no sistema biofloco com uma relação C:N de 10 apresentou o melhor rendimento de produção quando comparado aos outros tratamentos (CN15 e CN20).