Effects of different carbon sources on water quality, growth parameters and excretion of metabolic nitrogen in a biofloc -common carp (Cyprinus carpio) culture system

Biofloc system is a new technology that used in intensive and semi intensive aquaculture systems. The main advantage of this system is reducing the water use, along with increasing the intensity of production based on heterotrophic bacteria than autotrophic bacteria. The fish were divided into 4 groups in 3 replicates. The first group (A) was reared in normal culture situation as a control. In subsequent treatments, juvenile were rearing in a biofloc system containing various carbon sources, including: maize flour (B), Wheat flour (C) and barley flour (D) as different treatments. One hundred and twoenty fingerlings of common carp with initial average body weight of 15.18±2.07g introduced into the experimental treatments and cultured for 45 days. At the end of the experiment, water quality, growth preformance, and metabolic nitrogen excretion rates compared among treatments. Based on the results, water quality improved among all biofloc treatments compared to the control group (p<0.05). Growth indices significantly improved in all biofloc treatments (p<0.05). The highest growth rate and the lowest feed conversion ratio were recorded in the biofloc system containing barley flour (p<0.05). Ammonia and urea excretion in biofloc treatments were significantly higher than the control group (p<0.05). The highest ammonia and urea excretion rates were recorded in the biofloc treatment containing barley flour (p<0.05). Therefore, it was concluded that the use of barley flour as a carbon source in the biofloc system can be used for rearing of common carp. The use of this carbon source, in addition to improving of water quality, is effective in promoting the growth of common carp in the biofloc system..