Aquaponics is the combination of aquaculture (fish) and hydroponic cultivation of plants. This review examines fish welfare in relation to rearing water quality, fish feed and fish waste and faeces to develop a sustainable aquaponic system where the co-cultured organisms, fish, bacteria in biofilters and plants, should be considered holistically in all aquaponics operations. Water quality parameters are the primary environmental consideration for optimizing aquaponic production and for directly impacting fish welfare/health issues and plant needs. In aquaponic systems, the uptake of nutrients should be maximised for the healthy production of the plant biomass but without neglecting the best welfare conditions for the fish in terms of water quality. Measures to reduce the risks of the introduction or spread of diseases or infection and to increase biosecurity in aquaponics are also important. In addition, the possible impacts of allelochemicals, i.e., chemicals released by the plants, should be taken into account. Moreover, the effect of diet digestibility, faeces particle size and settling ratio on water quality should be carefully considered. As available information is very limited, research should be undertaken to better elucidate the relationship between appropriate levels of minerals needed by plants, and fish metabolism, health and welfare. It remains to be investigated whether and to what extent the concentrations of suspended solids that can be found in aquaponic systems can compromise the health of fish. Water quality, which directly affects fish health and well-being, is the key factor to be considered in all aquaponic systems.

The effects of 8 nutritional variables (Ca/P, Eicosapentaenoic acid (20:5n-3) + Docosahexaenoic acid (22:6n − 3) (EPA + DHA), Arachidonic acid (20:4n − 6) (ARA), Se, vitamins E, C, D and A) were investigated to identify their respective importance and interactions in pikeperch larval development. In this respect, two modalities (low and high levels) of each variable were tested through a fractional factorial experimental design allowing a reduction from 256 (2⁸) to 16 (2^8 – 4) experimental units. Survival was significantly higher in larvae fed a high Ca/P diet while larval growth was significantly lower in larvae fed the same diet variant, associated with a higher incidence of kyphosis and pectoral anomalies in these larvae. Lordosis and scoliosis seemed to be mostly affected by dietary long chain polyunsaturated fatty acids (LC-PUFAs). A significant interaction was shown between n-3 LC-PUFA and vitamin C on jaw anomalies, while myocyte-specific enhancer factor 2C (mef2c) gene expression correlated positively with dietary vitamin C increment. Results also demonstrated an effect of the different nutrients and their interactions on the activity levels of digestive enzymatic activities. The results of the present study highlight the importance of the interactions between Ca/P, LC-PUFAs and vitamins C and E, suggesting their essential roles as key nutritional factors influencing pikeperch larval development.