An experiment over 60 days assessed the impact of adding exogenous enzymes to the biofloc system with tilapia. A preliminary sludge hydrolysis experiment has been undertaken to fix the percentage of enzymes (amylase and protease) based on total solids (TS) level for which 4 doses (3,6,12,18% of TS) of a single enzyme (protease or amylase) and mixed enzymes (protease and amylase ) in 250 ml aquaculture sludge. The 6% mixed enzyme was found to impart a better sludge hydrolytic effect and was chosen for the second experiment. The 6 % of mixed exogenous enzymes were supplemented in different ratios to the sub culture of biofloc inoculum (1:1, 1:2, 1:3 and 1:4 enzyme/ TS as T1-T4) in triplicates to follow a completely randomized design. A conventional biofloc group was maintained as a control (BC). Floc volume is significantly influenced by enzyme-supplemented biofloc tanks than BC. Enzyme addition significantly influenced the inorganic metabolites in the culture media over BC. However, the maximum mean nitrate-N level was observed in T4. The mean weight gain (14.15 ± 0.03 and 13.97 ± 0.01 g), percentage weight gain (638.76 ± 1.17 and 630.25 ± 2.79 %), specific growth rate (3.33 ± 0.003 and 3.31 ± 0.01) and thermal growth coefficient (0.29 ± 0.0003 and 0.29 ± 0.0002) were significantly higher in T3 and T4 than others. The maximum feed utilization was found in entire treatment groups compared to the control and the survival rate was 100 % in T2 and T3. The study found that a 6% concentration of mixed enzymes (amylase and protease) can effectively improve the hydrolysis of inorganic metabolites and accelerate the somatic growth and feed utilization parameters of GIFT tilapia reared in saline ground water.
Keywords
Biofloc technology, Inorganic metabolites, Exogenous enzymes, GIFT Tilapia, Inland Saline,