In this study, we investigated the effects of swimming activity and feed restriction on juvenile rainbow trout (Oncorhynchus mykiss) in decoupled aquaponic systems. Our focus was on assessing their impact on water quality parameters within the aquaponic setup and evaluating the growth performance of the fish, including final weight (FW), condition factor (K), coefficient of variation (c.v.) in weight, specific growth rate (SGR), total feed intake (g/fish), feed conversion rate (FCR), hepatosomatic index (HSI), and viscerosomatic index (VSI), as well as the growth of lettuce (Lactuca sativa L. var. elmaria). The study involved 108 juvenile rainbow trout with an average initial weight of 26.54 ± 0.36 g and 60 ten‐day‐old lettuce seedlings, over a period of 42 days. We designed four treatment groups, each with three fish tanks: static ad libitum (SA), where fish were in static water conditions and fed to satiation; static restriction (SR), with fish in static water and a 25% feed restriction; current ad libitum (CA), where fish experienced forced swimming at 1 BL s⁻¹; and current restriction (CR), with swimming exercise at 1 BL s⁻¹ and a 25% feed restriction. Using a flow rate of 1 BL s⁻¹ in the tanks for rainbow trout yielded several benefits. Notably, the fish in the CA group exhibited increased feed intake (60 ± 1.78 g fish⁻¹) and enhanced fish growth with an FW of 91.72 ± 0.91 g, compared to the SA group (55.88 ± 0.88 g fish⁻¹ for feed intake and 89.26 ± 0.81 g for FW). In contrast, the CR group showed a reduced feed intake (39.02 ± 2.78 g fish⁻¹) and a lower FW (67.85 ± 1.49 g) compared to the CA group. In addition, the CA group demonstrated positive contributions to fish development with a reduced HSI (1.26 ± 0.02) in comparison to the SA group (1.56 ± 0.14). Inadequate nutrient provisioning in the SR and CR groups negatively impacted fish growth and system efficiency. Our findings suggest that optimizing water flow and feed benefits fish and plants and enhances system sustainability.

We investigated the effects of growth performance of three plant species parsley (Petroselinum crispum), lettuce (Lactuca sativa) and cress (Lepidium sativum) under the three different lighting sources, Light-Emitting Diode lamp (LED; 200w), High-Pressure Sodium lamp (HPS; 200w) and Fluorescent lamp (FLO; 200w) in an aquaponic system. A total number of 43 koi fish (Cyprinus carpio var. koi) with 3628 g total biomass (84.4 g per individual) were used. The fish used in the experiment recorded 36% growth and reached an average individual weight of 132.7 g at the end of the experiment. The parsley plant was measured as 8.76 ±7.32 g; 7.45 ±4.13 g; 2.04 ±1.96 g weight after 45 days, the lettuce plant was 54.09 ± 25.60 g; 60.83 ±19.39 g; 17.81 ±6.40 g weight after 54 days, cress plant was 1.03 ±0.58 g; 1.15 ±0.46 g; 1.31 ±0.58 g weight after 42 days, under the HPS, LED, and FLO light sources, respectively. HPS and LED light sources in lettuce and parsley showed better plant development than the FLO, while no significant difference occurred in cress plants under three light conditions. We conclude that using HPS or LED lights in indoor aquaponics has the potential to produce good quality and adequate amounts of plants.