Learning outcomes:
explain the methods which are used to farm large numbers of fish to provide a source of protein, including maintenance of water quality, control of intraspecific and interspecific predation, control of disease, removal of waste products, quality and frequency of feeding and the use of selective breeding.
Fish are farmed in fish farms because they are a good source of protein. Fish farms keep lots of fish in very small tanks to minimize space requirements. To stop the fish fighting with each other these precautions are taken;

- Different fish species are kept in separate tanks. This stops competition between species of fish (interspecific competition)
- Fish of different genders are kept separately (unless they are being bred)
- Fish of different ages are kept separately. This stops competition between fish of the same species (intraspecific competition)

As with the fermentation, the quality of the water is closely monitored and the fish are continuously supplied with fresh sterile water so that wastes are washed out constantly. The fish are kept in sterile water to limit disease, which would spread very quickly in the cramped ponds.
The fish are often over-fed, or fed with protein-rich food. Sometimes hormones are added to the water to speed growth. In addition to this only the biggest and most healthy fish are allowed to breed. This is an example of selective breeding.