Can Application of Commercial Microbial Products Improve Fish Growth and Water Quality in Freshwater Polyculture?

A 31-d experiment was conducted to examine the effects of three commercial microbial products (Novozymes pond plus, Zhongshui BIO-AQUA, and Effective Microorganisms) on production performance and water quality in freshwater tanks stocked with Grass Carp Ctenopharyngodon idellus, Gibel Carp Carassius gibelio and Silver Carp Hypophthalmichthys molitrix. Four treatments were used: blank control (BL), adding Novozymes pond plus (NO), adding BIO-AQUA (PB), or adding Effective Microorganisms (EM). The fish were fed daily with a formulated feed, and each of the microbial products was added to the tanks every 10 d. No significant differences were found in survival, weight gain, and feed conversion ratio of the fishes, Secchi depth, chemical water quality, and phytoplankton between the blank control and any other treatments (NO, PB and EM). This study indicates that the addition of these three microbial products every 10 d has limited function to improve production performance and water quality in freshwater polyculture of Grass Carp, Gibel Carp, and Silver Carp within the first 31 d of application. Received July 6, 2015; accepted October 30, 2015