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Biofloc technology system (BFT), recirculation aquaculture system (RAS) and polyculture promote efficient use of water, area and nutrient recycling, which are essential practices for sustainable aquaculture development. The aim of this study was to evaluate the growth, feed efficiency, biofloc composition and water quality of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in monoculture and polyculture with giant freshwater prawn Macrobrachium rosenbergii (De Man, 1906) in BFT and RAS, over a period of 30 days. Fish (n = 128; 7.29 ± 0.67 g) were distributed randomly in 16 experimental tanks (8 fish/tank). Prawn (n = 96; 0.50 ± 0.09 g) were allocated in 8 experimental tanks (12 prawn/tank) in a polyculture. The experimental design was completely randomized with four treatments with four replicates each, in a factorial design 2 9 2 (BFT and RAS vs. monoculture and polyculture). The experimental diet (28% of digestible protein; 3100 kcal kg-1 of digestible energy) was used both to fish and prawn in BFT and RAS. There was significant effect (p \ 0.01) of the system and the culture for weight gain, apparent feed conversion and protein efficiency ratio. The average weight gain and apparent feed conversion of tilapia in monoculture (30.04 g and 1.39) and in polyculture (36.44 g and 1.27) were superior (p \ 0.01) in BFT than in monoculture (23.64 g and 1.74) and in polyculture (24.14 g and 1.61) in RAS. Weight gain and survival of giant freshwater prawn was superior (p \ 0.01) in BFT (0.43 g and 87%) compared to RAS (0.26 g and 79%). The data showed that BFT provides better growth performance responses in monoculture for Nile tilapia and in polyculture with giant freshwater prawn compared to RAS.

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This study evaluated the modulation of the ventilatory frequency of Nile tilapia sedated with essential oil of Ocimum basilicum and eugenol. The fish were exposed to the following treatments: control (water only); ethanol 200 µl L-1 (concentration used to dilute the anesthetic); eugenol 10 µl L-1 and 20 µl L-1; essential oil of O. basilicum at the concentration of 10 µl L-1 and 20 µl L-1. After 90 minutes of exposure to the treatments, water quality, mortality and respiratory rate were determined. The concentration of 20 µl L-1 of the essential oil of O. basilicum and eugenol showed a sedative effect and reduced the excretion of metabolic ammonia in Nile tilapia. There was no mortality in fish exposed to the treatments. The respiratory rate did not differ between the different treatments. It is concluded that the concentration of 20 µl L-1 of the essential oil of O. basilicum and eugenol shows the best result in the inducing sedative effect for Nile tilapia, and that the essential oil of O. basilicum and eugenol in the concentrations of 10 µl L-1 and 20 µl L-1 in an exposure period up to 90 minutes do not alter the ventilatory frequency of Nile tilapia.