Fish management in an aquaponics system

Fish management

When growing fish in your aquaponics system, it is important to maintain good water quality. As an aquaponics grower you have the responsibility to keep your plants and fish healthy. Therefore, we investigate fish management in an aquaponics system.

Water quality considers several parameters. Temperature and pH first come to mind, followed by dissolved gases (oxygen and carbon dioxide) and dissolved nutrients such as ammonia (NH3), nitrite (NO2) and nitrate (NO3). Check how these parameters are relevant to the fish species that you want to produce. The table below is a water quality guideline for keeping tilapia.

Fish managementAs it is recommended for the plants, it is best to wait until the initial cycling process is totally completed and the biofilter is fully functioning to add the fishes to the system. System cycling is a term that describes the initial process of building a bacterial colony when first starting any aquaponics unit. Under normal circumstances, this takes 3–5 weeks; cycling is a slow process that requires patience. Overall, the process involves constantly introducing an ammonia source into the aquaponics unit, feeding the new bacterial colony, and creating a biofilter. The progress is measured by monitoring the nitrogen levels using the nitrate test kit. If it is decided to add fish before cycling, then a reduced number of fish should be added. This time will be very stressful for the fish, and water changes may be necessary.

Fish selection:

Several fish species have recorded excellent growth rates in aquaponics units. Fish species suitable for aquaponics farming include tilapia, common carp, koi-carp, silver carp, grass carp, barramundi, jade perch, catfish, trout, salmon, Murray cod, and largemouth bass.

It is also important to be aware of local regulations governing the importation of any new species. Exotic (i.e. non– native) species should never be released into local bodies of water. Local extension agents should be contacted for more information regarding invasive species and native species suitable for farming.
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Author

  • Manager, Aquaculture, Department of Animal Sciences, Stellenbosch University

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