Chitosan Foam–Based Filter: Maintenance of Water Quality for Nile Tilapia Cultivation

The objectives of this research were to evaluate the maintenance of water quality when using chitosan foam filters in water recirculation systems during the cultivation of Nile tilapia and to verify the zootechnical performance and the hepatic and branchial histopathological changes, in comparison with the use of biological filter with bioballs. Two Nile tilapia cultivation trials were carried out (trial 1: 35-L tanks; trial 2: 130-L tanks), using six individual water recirculation systems, consisting of a culture tank, decantation tank, submerged pump for recirculation, aeration and external filter. The physical and chemical parameters related to water quality were evaluated every 48 h. At the end of each trial, the fish biometrics was performed to obtain final weight, feed conversion, and survival. In trial 2, the histopathological analysis of the hepatopancreas and gills was performed and the organ index was calculated. The daily averages of the physical and chemical parameters of the water quality, the zootechnical performance of the fish, and the organ indexes of the treatments of trials 1 and 2 were compared by the t test (p ≤ 5%). There were no significant differences in final weight, feed conversion, survival, or organ indexes between treatments (p > 0.05) in relation to the two trials. It was observed that the use of the filter with chitosan foam in the water recirculation systems resulted in lower or equal concentrations of total ammonia, nitrate, and dissolved orthophosphate, and maintained the same or higher alkalinity than in tanks with bioball biological filter. It is recommended to change the chitosan foam every 30 days of cultivation. The use of water recirculation systems with treatment using filters filled with chitosan foam during the cultivation of Nile tilapia is equally effective or better than the use of a biological filter with bioballs.