To mitigate the serious water pollution caused by the rapid expansion of the aquaculture industry in
recent years, the development of improved aquaculture systems with more efficient water usage and
less environmental impact has become essential. In this study, a land-based recirculating aquaculture
system (RAS) was established that consisted of purification units (i.e., a primary biological pond, two
parallel horizontal subsurface flow constructed wetlands [CWs], and a long ecological ditch) and 4–5
series-connected recirculating ponds. This system was mainly designed to stock channel catfish (Ictalurus
punctatus), fifteen spine stickleback (Spinibarbus sinensis) and yellow catfish (Pelteobagrus fulvidraco),
and the culture efficacy was evaluated based on a 2-year field experiment covering two growing seasons.
According to the results, the primary biological pond played a role in sedimentation or nutrient retention,
although this was not as evident when the CWs were functioning. The water flowing through the
wetland system at a hydraulic loading rate (HLR) of 600 mm/day displayed lower values for the temperature,
pH, dissolved oxygen (DO), suspended solids, organic matter and nutrients, whereas the electrical
conductivity (EC) was higher, suggesting the accumulation of dissolved solids in the system. Due to the
recirculation treatment, the trophic status of the recirculating ponds increased gradually along the direction
of the flow and was notably lower in comparison to the control. As a result, the fish production
responded to the variation of the water quality, which was reflected in the measurements of culture
efficacy (final weight, survival rate, SGR and yield). The three main rearing species showed a decreasing
trend along the direction of the flow, which was higher compared to the control, whereas an opposite
trend was observed for filter-feeding fish. A Pearson correlation analysis revealed that the main culture
species were inclined to live in meso- or oligotrophic conditions, and the silver carp adapted to more
eutrophic conditions. Because RAS can provide better environmental conditions year-round, the present
culture method could be more suitable for species that are sensitive to water quality in typical subtropical
areas.