Material and methods
Fish
A total of 2400 O. niloticus fries (mean individual initial weight 4 ± 1.0 g) were divided into six equal groups, each consisting of four replicates (100 fry/replicate) in 6 separate earthen ponds. Fish in each replicate were reared in a hapa made of cotton mesh like a cage (3 × 2 × 1 m, each) that was fixed in an earthen pond (for each group, a total of 4 hapas were equally arranged in 4 rows).