Author(s): Purna Chandra Das, Sayan Mandal and Basudev Mandal

Abstract: The experimental work focused on 90 days culture of Heteropneustes fossilis in the 1000lit biofloc (T1&T2) and non biofloc (C) system to observe growth and production with lowest possible water exchange. And also observe the isolation and enumeration of microorganism. The stocking density was 500fish/1000lit water in all tanks. Species reached 4.3 to 22.5gm, in T1, 24.0 in T2 tank and 18.5gm in C tank. The survival rate also high in T1&T2:88-95%and C tank it was80-90% and the FCR was1.5 in C and 0.6&0.8 in T1&T2 tanks respectively. The total weight gain and specific growth rate per day was in T1,T2 and C tanks 18.2, 20.0and 14.2gm&0.74,0.69and0.57respectively. Temperature ranges 26-32.5°C in all tanks. In biofloc tanks (T1&T2), pH has been found: 7.4-8.0, Dissolve Oxygen:4.8-5.9ppm, Free CO2:4.2-4.5ppm, Alkalinity:295-300ppm, Ammonia:0.15-1.0ppm, Nitrate:0.00-10.5ppm, Nitrite:0.25-1.5ppm, TDS:1500-1900ppm. Whereas in C tank pH range: 6.5-7.6, Dissolve Oxygen:5.2-5.5ppm, Free CO₂:4.2-4.6ppm, Alkalinity:278-287ppm, Ammonia:0.07-1.2ppm, Nitrite:0.01-0.1ppm and TDS:1000ppm. Mean value of all types of bacterial colony forming unit /ml in experimental T1&T2 tanks was Anaerobic bacteria:11×10⁶,Gram negative bacteria;9×10⁴, Bifidobacterium sp 176×10³, Pseudomonas sp:9.5×10³, Vibrio sp:742×10³, Nitrifying bacteria:1.8×10³. Moreover, water exchange of 20% in T1 & T2 tank and 50% in C tank required in every week.

DOI: 10.22271/fish.2021.v9.i3c.2480

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