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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.

The objective of this study was to evaluate the performance of Nile tilapia and the lettuce, watercress, and arugula vegetables in a gravel-bed aquaponic system using the aerated fish tank-to-vegetable growing bed volume ratios of 1:1 and 1:2. Each experimental unit consisted of an aquaponic module composed of two containers: one to allocate the vegetables (500-L tank with gravel, measuring 2 m2) and another to stock fish at the ratios of 1:1 (500-L vegetable:500-L fish tank) and 1:2 (500-L vegetable tank:1000-Lfish tank). The experiment was laid out in a randomized-block design with two treatments (500-L fish tank × 1000-L fish tank) and three blocks (periods). The performance of the Nile tilapia and of the vegetables did not differ significantly in response to the increasing fish tank volume, with the fish and the vegetables exhibiting good performance results in both volume ratios. In conclusion, in aquaponics, the fish tank-to-vegetable tank volume ratios of 1:1 and 1:2 are equally effective for the production of Nile tilapia and the lettuce, watercress and arugula vegetables.

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