The FCR values in in-situ biofloc treatment was less compared to the control treatment. SGR (Specific Growth Rate) value was more in in- situ treatment compared to control one. FCR, SGR and net fish yield (kg h-1 in different treatments was presented in (Table- 2).
Experiments were carried out in nineteen FRP tanks (1000 L each) for a period of 90 days. The experimental design included in-situ biofloc and control treatments conducted at three different stocking densities (STD) 25, 50 and 75 no. fish per m3 of tank respectively with each experiment replicated thrice.
IMC of individual average weight 15± 1.6 g was reared in all treatments. In in-situ biofloc treatment, low protein (20%) commercial fish feed was added initially. Further, organic carbon in the form of wheat flour was added daily to maintain the C:N ratio at 10 . The amount of feed and extra carbohydrate required in biofloc process varies with time as biomass density varies with time. Around 60% extra carbohydrate to be applied in a typical in-situ biofloc tank. In control treatment, high protein (30%) commercial fish feed was added. In all the treatments, TAN concentration was kept below 1 mg L-1 through 50% water exchange whenever required (Table-1). Feeding rate, water quality parameter and fish growth parameter were determined following standard methodology. TSS and BOD levels were more in in-situ biofloc treatment as compared to the control treatments. The harvested weight of fish in in-situ biofloc treatment with STD 25 no./m3 were found to be significantly higher among all the treatments (p <0.05). The results achieved in the study confirmed the trends of decrease in growth for IMC species with increased stocking densities. During the 90 days culture period net fish yield was highest (3905± 234) in externally added biofloc tank with highest stocking density (STD 75 no/m3). Fish survival was 100% in all the treatments.
Biofloc technology is a method for improving water quality in aquaculture by maintaining a balance of carbon and nitrogen in the system. The technology has recently gained attention as a sustainable method to control water quality, with the added value of producing proteinaceous feed in- situ. The present study was conducted to compare the effects of in-situ produced biofloc on the growth and production of IMC under different stocking densities in light limited Indore tank.