Alkaline and acid phosphatases in a tank water rearing carp (Cyprinus carpio)

Alkaline and acid phosphatase activities were successively measured to understand their relation to water quality parameters and bacterial population in a carp rearing tank equipped with a recirculating water system. As a result, it was shown that the alkaline phosphatase activity fluctuated in accordance with the changes of almost all water quality parameters which reached stability at 2 weeks after the beginning of experiment. Additionally, the alkaline phosphatase activity was closely related to the direct viable count which represents the active bacteria present in the water. On the other hand, acid phosphatase activity generally showed no close relationship with water quality parameters. These results strongly suggested that the alkaline phosphatase activity can possibly become a good parameter for water quality assessment of fish rearing conditions