Abstract:The bioflocs can be used as an addition of high value feed by fish or shrimp. Water quality can be improved, and pathogenic bacteria can be controlled, thereby reducing the potential spread of diseases, and feed conversion ratio can be reduced in biofloc technology systems. Mirror carp, Cyprinus carpio, as a bottom fish, are popular with culturists because of its ease of breeding, fast growth, and tolerance to wide range of environmental conditions and resistance to diseases. The species is also ideal for use in polyculture systems because of its mild behavior and broad diet. Similarly, silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis), are the typical filter-feeding fish, which have drawn much attention worldwide because of their importance as aquaculture species as well as their potential for the biomanipulation of plankton communities. The multitrophic approach of combining species with different specific feeding niches maximizes resource utilization more efficiently than monoculture. However, there is little documentation on practicability of using biofloc technology for bottom and filter feeding carp in minimum water exchange pond polyculture systems. Therefore, a 90-day experiment was conducted to examine the effects of carbon source addition on water quality and growth performance of fish in different carp stocking modes land-based experimental mesocosm biofloc systems. Three stocking modes with mirror carp monoculture, mirror carp + bighead carp polyculture, and mirror carp + bighead carp + silver carp polyculture were arranged in three replicate enclosures. The results showed survival rates (SR) of mirror carp in polyculture mode were significantly higher than that in monoculture mode, and protein efficiency ratios (PER) of fish in two species and three species polyculture modes were 30.1% and 36.1% higher than that in monoculture mode, while the total feed conversion rates (TFCR) of fish were 22.7% and 26.3% lower than that in monoculture mode. The crude protein and ash of the muscle composition of mirror carp in three species polyculture mode were significantly higher than those in monoculture mode. The results showed a significant positive correlation between bioflocs volumes and experimental water temperatures at the temperatures of 19.3-28.5℃ in different stocking modes. The total ammonia nitrogen (TAN), nitrite nitrogen (NO2-N), total inorganic nitrogen (TIN), orthophosphate (PO4-P) and total suspended solidities (TSS) in two species and three species polyculture modes were lower than those in monoculture mode, while the nitrate nitrogen (NO3-N), total alkalinity, total suspended organics (TSO) and Chlorophyll a were higher than those in monoculture mode, and there were no significant differences in these parameters except for the Chlorophyll a between different stocking modes. The present study revealed that polyculture modes can effectively perform the ecological function and increase aquaculture efficiency in biofloc systems.