ResumoA avaliação da proporção ideal de concha calcária/brita em biofiltro no cultivo de pós-larvas de tilápia do Nilo foi o objetivo deste trabalho. O experimento foi realizado no Laboratório de Aquicultura e Ecologia Aquática da Universidade Federal dos Vales do Jequitinhonha e Mucuri -UFVJM, entre os dias 21 de julho a 3 de agosto de 2011. Pós-larvas de tilápia do Nilo na densidade de 13,3 pós-larvas/L foram cultivadas em aquários contendo biofiltros com 100% concha calcária; 70% concha calcária/30% brita; 50% concha calcária/50% brita; 30% concha calcária/70% brita; 10% concha calcária/90% brita; 100% brita e como controle, aquário sem biofiltro, em DIC, totalizando sete tratamentos com três repetições. A presença de concha calcária no biofiltro proporcionou melhores condições da água, quando comparado com os aquários sem biofiltro e com brita apenas, mantendo os parâmetros adequados para o cultivo de tilápia do Nilo. Apesar dos níveis de amônia estarem próximos ao limite superior desejado para o cultivo da espécie, eles não comprometeram o crescimento (comprimentos total e padrão, altura e peso). A proporção 30% de concha calcária e 70% de brita é recomendada como substrato de biofiltro, por apresentar a melhor taxa de nitrificação ao longo do experimento.
Palavras-chave: biofiltração, larvicultura, nitrificação, resíduos nitrogenados, Oreochromis niloticus.
AbstractThe evaluation of the optimal ratio of calcareous shell/gravel substrate in biofilters was evaluated in post-larval culture of Nile tilapia the was objective of this work. The experiment was conducted at the Laboratory of Aquaculture, UFVJM University, Brazil, from July 21 to August 3, 2011. Post-larvae of Nile tilapia at density 13.3 post-larvae/L were grown in tanks containing biofilters with 100% calcareous shell; 70% calcareous shell/30% gravel; 50% calcareous shell/50% gravel; 30% calcareous shell/70% gravel; 10% calcareous shell/90% gravel; 100% gravel; tank without biofilters and control, in completely randomized design with seven treatments and three repetitions. Calcareous shell provided better water conditions than tanks without biofilter or containing only gravel, keeping the parameters suitable for Nile tilapia farming. Although ammonia levels were close to the desired upper limit, they had no influence on morphological parameters (total length, standard length, height and weight). The rate 30% shell/70% gravel is recommended as biofilter substrate, as it provided the best nitrification rate during the experiment.
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