Coupled vs. decoupled aquaponics: Evidence, mechanisms, and methodological gaps in the productivity hypothesis

Aquaponics integrates recirculating aquaculture systems (RAS) with hydroponic plant cultivation with the goal of creating a more resource-efficient food production strategy. A central question in aquaponic design is whether system performance is improved when aquaculture and hydroponic units are hydraulically coupled in one loop or decoupled into independently managed modules. This review evaluates that question through a systems and microbial-ecological lens, with emphasis on productivity, nutrient-use efficiency, and resilience outcomes. Current evidence does not support a consistent productivity advantage for either coupled or decoupled configurations. Reported differences are frequently confounded by nutrient loading, solids management, hydraulic retention time, species selection, environmental control, and site-specific operating conditions. Microbial effects are likely important, but most studies remain taxonomic rather than functional, limiting mechanistic interpretation. Overall, configuration should be treated as one design variable within a broader operational framework rather than as a stand-alone predictor of yield or robustness.