The rotifer Brachionus plicatilis is a universal live feed in marine fishes and crustacean larval hatcheries as their first live diet. The mass production of this rotifer in tropical hatcheries is unpredictable due to sudden crush and limited facilities in order to produce high quality microalgae. Recently developed biofloc based system is considered a potentially viable technique that proliferates natural probiotic bacteria and various microorganisms along with rotifer, Brachionus but the monoculture of rotifer has not initiated in a biofloc system. A 4-days rotifer B. plicatilis batch culture was conducted in biofloc system using molasses, rice bran, maize starch, palm kernel expeller versus a control (without carbon source). This study was maintained the carbon:nitrogen ratio at 10.
Daily water quality parameters and rotifer population density were evaluated. Fifteen 125 L polyethylene tanks with water volume of 100 L were used for this experiment. Each tank was stocked with 5×106 rotifer (50 rotifer ml-1). Each treatment was randomly assigned in triplicate. TAN concentration and pH values were significantly lower in the four biofloc systems than control (p < 0.05) (Table 1). Significantly higher biofloc volume was obtained in the molasses and rice bran adding biofloc systems than those adding the maize starch or palm kernel expeller (p < 0.05) (Table 1). Significantly higher B. plicatilis population density and their specific growth rate were in the molasses and rice bran adding bioflocs treatments (p < 0.05) and these were followed by palm kernel expeller, maize starch and control, respectively (Table 2). The present study indicated that molasses and rice bran carbon source enhanced the production of B. plicatilis in the biofloc system.