Aquaponics provides an alternative opportunity for the combined production of fish and plants. Most of the essential nutrients required for optimal plant growth can be supplied from the fish feed, except for K and Fe. These nutrients are usually inadequate in fish feed. In this study, red tilapia and rocket plants were co-cultivated in an aquaponics system along with the extra addition of K and Fe. Fish growth, morpho-anatomical characteristics, and K and Fe loading on fish gills were studied. Plant growth parameters were also determined. The addition of Fe and K slightly improved the produced fresh biomass of rocket per unit area and had no impact on tilapia growth and survival. No severe histological alterations in fish gills, liver, and midgut were detected. EDX analysis showed that the addition of K led to the enrichment of this specific ion in fish gills, but no effects of this accumulation were found on other aspects of fish growth and survival.

Brackish aquaponics using Mediterranean fish and plants provides an alternative opportunity for a combined production of high-quality food products with high commercial and nutritional value. This is the first study that investigates the effect of two different salinities (8 and 20 ppt) on growth and survival of Sparus aurata and Crithmum maritimum along with the cellular stress pathways using the activation of heat shock proteins (HSPs) and mitogen-activated protein kinase (MAPK) protein family members and the water bacterial abundance. In total, 156 fish were used (average initial weight of 2.55 g, length of 5.57 cm) and 36 plants (average initial height of 8.23 cm) in floating racks above the 135 L fish tanks. Survival rate for both organisms was 100%. C. crithmum grew better at 8 ppt (t-test, p < 0.05). The growth rate of S. aurata was similar for both treatments (p > 0.05). HSPs and MAPK were differentially expressed, showing tissue-specific responses. The average bacterial abundance at the end of the experiment was higher (p < 0.05) in the 20 ppt (18.6 ± 0.91 cells × 10⁵/mL) compared to the 8 ppt (6.8 ± 1.9 cells × 10⁵/mL). The results suggest that the combined culture of euryhaline fish and halophytes provides good quality products in brackish aquaponics systems.

The aim of this study is to investigate the effect of 10 and 20% replacement of fishmeal (FM dietary group) with the superworm Zophobas morio larvae meal (ZM10 and ZM20 dietary groups) on the growth performance of sea bass (Dicentrarchus labrax) and lettuce plants (Lactuca sativa) reared in aquaponics. Ninety juvenile sea bass with an average body weight of 21.55 g/individual were placed in aquaponic fish tanks, together with 24 lettuce plants with an average initial height of 8.90 cm/plant and an average number of leaves of 5.75/plant over a 45-day trial period. At the end of that period, all feeding groups exhibited high survival. In fact, ΖΜ10 and ZM20 groups showed similar fish weight gain and specific growth rate (SGR) (p > 0.05), but significantly lower SGR (p < 0.05) than the FM group. Nevertheless, final fish body weight and length were similar (p > 0.05) for all feeding groups. No plant mortality was observed during the 45-day study period. All three aquaponic systems resulted in similar leaf fresh weight, as well as fresh and dry aerial biomass. At the end of the experimental period, plants in the third system showed higher fresh leaf weight, total weight of fresh leaves, total dry aerial biomass, and total produced biomass compared to the other two systems. The results of the present study show that fish fed with the ZM10 diet had higher weight gain (WG) than fish fed with the ZM20 diet, while the SGRs for ZM10 and ZM20 were similar. Both ZM10 and ZM20 diets result in efficient lettuce production. This study also provides data that enlighten the feasibility of integrating insect meals as fish feeds for aquaponics which helps towards the development of an ento-aquaponic approach.