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.
With intensive fish farming there is extra aeration with ‘paddle wheels’ and addition of feed. This results in productions rates up to 10 times that of extensive farming. Ponds are enclosed systems, but discharge water is let out in channels, rivers or sea. 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.