Extensive to semi-intensive aquaculture systems produce the bulk of aquaculture products. Extensive farming usually involves unsophisticated technology, relies on natural food and has a low input to output ratio. Usually only a part of the life cycle is controlled, for example extensively operated fish ponds often rely on the supply of fish juveniles from the wild, and production inputs, in the form of feed and fertilizers, are provided only occasionally, if at all. Preparation of fish feed for pond aquaculture of local catfish near Phnom Penh, Cambodia. The system found most frequently is the farming of fish in ponds, but rice-fish farming or the stocking of fish into natural or impounded water bodies are also included.
Intensive systems produce more output from a given production unit.
This is achieved through higher levels of technology and a greater degree of management. Fish or other aquatic organisms are often reared from egg to adult stage within the culture facilities, stocked at higher densities, and in smaller, well-designed facilities. With increasing stocking densities, chemical prophylactics are more commonly used to prevent disease. Compound, manufactured feed in the form of pellets is provided on a regular basis. Water quality is carefully controlled with the aid of filters, purifiers, pumps and aerators.