Healthy C. punctatus (18−20 g in weight; 9−11cm in length) were collected from local freshwater bodies in and around Annamalai University, Annamalainagar. Fish were separately maintained at 27±1°C in 1,000 L tank with continuously aerated and dechlorinated tap water (pH 7.2−7.4; hardness 185-200 mg L-1 as CaCO3; alkalinity 170−175 mg L-1 as CaCO3) at least one month prior to the experiments.
The laboratory photo period was 12 h D: 12 h L. Fish were fed with boiled chicken eggs and small pieces of earthworm on alternate days and then 60% water was renewed everyday