Use of commercial probiotics for the improvement of water quality and rotifer density in outdoor mass culture tanks

An experimental study was carried out to evaluate the efficacy of three commercially available probiotics P1, P2 and P3 consisting of mainly Bacillus spp. and nitrifying bacteria against Vibrio loads in mass culture tanks of the rotifer Brachionus plicatilis. Triplicate tanks were maintained for each of the probiotic treatment as well as for control group. All the tanks were inoculated with 50 rotifers ml-1 and were fed with Nannochloropsis oculata at a density of 1 x 107 cells ml-1. Every alternate day, all the experimental tanks were treated with probiotics at a concentration of 1 x 104 cfu ml-1 and the experiment was carried out for one week. The study showed a significant increase in rotifer density (p<0.05) in all the tanks treated with the probiotics and a maximum density of 400 nos. ml-1 was observed in the tanks treated with P3. After 5th and 6th day of culture, total elimination of Vibrios was also recorded in the tanks treated with P3 and P2 respectively. The study revealed that P3, with a combination of Bacillus, Thiobacillus, Acetobacter and Paracoccus supplemented with enzymes, was found to be most effective in the enhancement of rotifer density and also in the elimination of Vibrios in rotifer mass culture tanks.