Evaluating the water quality changes and formation of Bio-Floc in a zero-exchange water of common carp (Cyprinus carpio) culture system using different ratios of carbon to nitrogen (C:N)

Abstract

The Bio-Floc has more efficacies compared to fixed Bio-film for removing the nitrogen compounds in water recirculating fish culture system. In this trial, a completely randomized experimental design was run to evaluate the roles of three different ratios of carbon to nitrogen (C:N) including 10 (treatment 10 = T10), 15 (T15) and 20 (T20), into the carp culture systems on growth and water quality. The mean individual weight was significantly higher in T20 compared to the other treatments. At the end of the experiment, the fish attained from 70 to 552.8, 704.7 and 708.8 g in T10, T15 and T20, respectively. The FCR, ammonia and nitrate concentrations were significantly higher in T10 compared to the other treatments (p<0.05). Concentration of ammonia in T10, T15 and T20 were 78, 29.9 and 29.9 mg/L, respectively. A depletion trend was recorded in pH in all treatments during the experimental period. The electrical conductivity (EC) and Bio-Floc formation rate increased in all treatments and was significantly higher in T20. The EC of water were 1327.5, 1419.83 and 1419.83 mmos/cm in T10, T15 and T20, respectively. The rates of Bio-Floc reached to 71, 143, 163 mL/L in T10, T15 and T20, respectively. The results of this experiment indicated that using molasses to adjust C:N ratio of water at 20, enhances formation of Bio-Floc, carp growth rate and water quality in a zero-exchange water system.

Keywords

• c:n ratio
• bio-floc formation
• heterotrophic bacteria
• water quality
• common carp