The aquaponic principle is the coupling of animal aquaculture (e.g. fish) with plant production (e.g. vegetables) for saving resources. At present, various definitions of aquaponics exist, some bearing the risk of misinterpretation by dismissing the original meaning or being contradictory. In addition, there is no standard terminology for the aspects of coupling between the aquaponic subsystems. This study addressed both issues.

This research aimed to developed new or revised definitions that are summarized by: aquaponic farming comprises aquaponics (which couples tank-based animal aquaculture with hydroponics) and trans-aquaponics, which extends aquaponics to tankless aquaculture as well as non-hydroponics plant cultivation methods. Within this conceptual system, the term aquaponics corresponds to the definitions of FAO and EU. A system analysis approach was utilized to explore different aquaponic setups aiming to better describe the way aquaponic subsystems are connected.

New terms were introduced, such as ‘coupling type’ and ‘coupling degree’, where the former qualitatively characterizes the water-mediated connections of aquaponic subsystems. A system with on-demand nutrient water supply for the independent operating plant cultivation is an ‘on-demand coupled system’. The coupling degree comprises a set of parameters to quantitatively determine the coupling's efficiency of internal streams, for example, water and nutrients. This new framework forms a basis for improved communication, provides a uniform metric for comparing aquaponic facilities, and offers criteria for facility optimization. In future system descriptions, it will simplify evaluation of the coupling's contribution to sustainability of aquaponics.

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Baganz, GFM, Junge, R, Portella, MC, et al. The aquaponic principle — It is all about coupling. Rev Aquac. 2021; 14: 252– 264.