Composite fish culture
Stocking several carp species in one pond so that each feeds at a different level, making full use of the pond's food.
Also: polyculture of Indian major carps, polyculture
Polyculture means raising several species together. In India's composite fish culture, developed in the 1970s, a pond is stocked with the three Indian major carps and up to three Chinese carps. Silver carp and catla filter plankton near the surface, grass carp eats weeds and fodder, rohu feeds in the middle water, and mrigal and common carp feed on the bottom. Because they do not compete much, one pond yields more fish than any single species would. The grass carp's droppings also fertilise the pond for the plankton eaters.