Comparative Analysis of Eel (Anguilla japonica) Growth Performance and ‘Caipira’ Lettuce (Lactuca sativa) Productivity in Relation to Nitrogen Concentrations Across Aquaponics, FLOCponics and Hydroponics Systems

This study compared conventional aquaponics (AP), biofloc-based aquaponics (FLOCponics, FP), and hydroponics (HP) in terms of juvenile eel (Anguilla japonica) growth, ‘Caipira’ lettuce (Lactuca sativa) productivity, and water-quality characteristics. The AP and FP treatments each comprised three replicate fish tank–plant cultivation systems stocked with 119 eels per tank, whereas HP was included as a control for plant production. Eels reared in FP exhibited a higher estimated final biomass and specific growth rate and a lower feed conversion ratio than those reared in AP. The total and shoot biomass of lettuce were higher in FP than in AP and were comparable to those obtained in HP.