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Aquaponics is the integration of aquaculture (fish) and hydroponic culture (plants) as one system. Aquaponics requires a sound simultaneous understanding of two agricultural ecosystems (fish and plants) in order to have a viable system. Modelling and model development is sacrosanct in systems where productivity is uncertain or complex. The study was conducted in 2016 to collect aquaponics information in the Republic of South Africa (RSA) using an online survey questionnaire to determine local aquaponics uses, management and distribution. A total of 44 aquaponics operators were captured within three months (September-November) in 2016. In this study, it was shown and concluded that most aquaponics practitioners in RSA do not have adequate knowledge and skills in aquaponics production and management, and that development of the localised aquaponics model is important for South Africa. As a result, the aim of this study was to develop a model that is more specific to South African conditions in order to help South Africans to have a better opportunity to establish and operate aquaponic systems. This study was designed as a mixed approach combining different methods and sources of data to develop the model. Unified Modelling Language (UML), Microsoft excel, an online survey, observations, structured and unstructured interviews and content data were used. The developed model was able to predict the main aquaponics inputs variables, namely fish stocking density, daily fish feed, and required planting area. The fit for each of these variables was good to average with R=0.7477, 0.6957, and 0.4313 respectively. There were no significant differences (P<0.05) between the observed and simulated data for all variables (fish stocking density, daily fish and planting area variables). Therefore, it was concluded that this model can be adopted by aquaponics practitioners in RSA and extension officers or facilitators as an aquaponics start-up platform.

Aquaponics have related food and nutrition security benefit that are important for this country (South Africa). The aim of this study was to apply aquaponics decision-making tool to provide potential aquaponics production data and information for South Africa. This study was designed as 2×3×3 factorial study giving 18 interactions. Because aquaponics are the production of fish and crops concurrently, yield production had two levels- fish and crop, fish stocking density had three levels- low, optimum and higher and aquaponics scale of production had 3 levels- hobby, subsistence and commercial scale. The summary of data of aquaponics variables from the literature was used as optimum level, lower and higher levels were based on experimental design. Yield production (kg) of both fish and plants increased significantly (p<0.05) as fish stocking density was increased. In hobby scale, plants yield was higher than fish yield in all levels of fish stocking density, the plant-fish yield (kg) was 40-33, 80-67 and 150-133, respectively. In subsistence scale, fish-plant yield (kg) was 240-200, 300-267 and 400-333, respectively. In commercial scale, fish-plant yield (kg) was 600-533, 1 100-1 000, 1 500-1 333, respectively. Daily fish feed increased significantly with increase in fish stocking density across all scale of aquaponics production (hobby<subsistence<commercial). In hobby scale, at low fish stocking, 0.65kg feed produced 1 kg fish, at optimum, 0.65kg feed produced 1 kg fish and at higher fish stocking, 0.37kg feed produced 1 kg fish. In subsistence scale at low fish stocking density, 0.38kg feed produced 1 kg fish, at optimum level, 0.63kg feed produced 1 kg fish and at higher level, 0.65kg feed produced 1 kg fish. In commercial scale, in low fish stocking, 0.64kg feed produced 1 kg fish, at optimum, 0.63kg feed produced 1 kg fish and at higher fish stocking, 0.64kg feed produced 1 kg fish. Plant culture have more yield output than fish culture in all aquaponics scale of production. Hobby scale produced the lowest yield than subsistence than commercial scale of production. Hobby scale practise could not produce sufficient yield to support human subsistence. Fish feed closely mirrored yield production. Lower fish stocking density maybe adopted in subsistence scale. Higher fish stocking density maybe adopted in commercial scale. Fish feed could become an economic sustainability constraint in aquaponics production, particularly in a developing country like South Africa. Water availability and quality effects on yield was not determine especially in African context. Key words: Fish stocking density, Yield production, Fish feed, Planting area