The effect of periphyton substrate density on production in freshwater polyculture ponds

The present research investigated the optimum surface area of periphyton substrate in earthen ponds stocked with a pre-optimized density and ratio of the Indian major carps, catla (Catla catla), rohu (Labeo rohita) and kalbaush (Labeo calbasu) to support enhanced fish production. Four treatments in triplicate were tried: no substrate (control), bamboo submerged substrate equal to 50% (treatment S-50), 75% (S-75) and 100% of the pond surface area (S-100). Water temperature ranged between 17 and 28°C, which is relatively low for tropical fish culture. Secchi disc depth and total ammonia concentrations were higher in control treatment than in substrate treatments. The average dissolved oxygen concentrations were higher than 5 mg l-1 in all treatment ponds and never fell below critical levels.…