Earth ponds are the most used unit for fish production worldwide, and more than 40% of world aquaculture production is performed in ponds. Ponds are used both for fish and shellfish and at different life stages. Important species grown in ponds, include different types of carp, catfish, shrimps and prawns. Ponds are normally used in extensive production and to some extent in more intensive production; here, however, the construction is less optimal.
An earth pond for aquaculture farming is usually defined as a pond where a natural ecosystem is created inside. This is the major difference between earth ponds and other closed production units, and the reason why they are described separately. The water exchange in the pond is normally very small and it will also function as a settling pond, so faeces and particles will settle on the bottom. There will be none or very little self-cleaning in the pond. When establishing the pond this must be taken into consideration, so that there is some spare capacity.
Inside the pond there can be a monoculture or polyculture. If using a polyculture, the natural food created in the pond (phytoplankton, zooplankton, aquatic insects, benthic organisms and the vegetation) can be utilized optimally by different species.