Fish farming is commonly described as being extensive, semi-intensive or intensive. These terms are not sharply defined but are generally related to the level of inputs of feed and/or fertiliser and to stocking densities.
In extensive pond farming there is zero or little feed added. Fish or shrimp live from algae and zooplankton that naturally grow in the pond. The growth of this natural feed can also be stimulated by addition of fertilizers. Feed conversion ratio (FCR) is high in extensive systems. Production of extensive farms are low. Without water treatment discharged water, which can contain antibiotics and high nutrients, has high environmental impacts. Destruction of important nature areas, such as mangrove forest, is a big issue.