2.3. Experimental design
Healthy rohu (L. rohita) showing no signs of disease (gross and
microscopic examination of skin, gills, and kidney tissues of representative
samples), with no previous history of parasitic infections,
and having a mean body weight of 60 g were obtained from Mannal
fish farm, Thanjavur, Tamil Nadu, India and acclimatised to laboratory
conditions for 2 weeks in 500-L plastic quarantine tanks at
28 2 C. All the fish were fed with control diet during the acclimatisation
period. About 20% of thewater in all tankswas exchanged
daily and 100% of the water was exchanged once a week. The basic
physicoechemical parameters of the water were measured every
week [19]. The O2 and ammonia concentrations ranged from 6 to
7.5 mg L1 and .04e.06 mg L1 ppm, respectively, and pH ranged
from 7.0 to 8.0 throughout the study period.