Lettuce production in a DWC aquaponic system with and without bioflocs compared to a hydroponic system in southern Brazil

Three recirculation systems – aquaponics (Aqua), aquaponics with bioflocs (AquaFloc), and hydroponics (Hydro) – were established to evaluate lettuce production (floating) over 45 days. Juveniles of hybrid tambacus kept in aquaponic tanks were fed commercial feed. Water quality was monitored and vegetable growth was assessed. Metrics of lettuce, such as head diameter, height, fresh matter, dry matter, number of leaves, and chlorophyll concentration, were significantly higher (p < 0.05) in the Hydro system than in the AquaFloc system even after 60 days. The AquaFloc system exhibited 62% fish survival, significantly lower (p < 0.05) ammonia and nitrite concentrations than Hydro, and an absence of nitrate. Electrical conductivity and total dissolved solids concentration were significantly lower (p < 0.05) in AquaFloc than in Hydro, while pH levels were significantly higher (p < 0.05) in both Aqua and AquaFloc, resulting in reduced nutrient availability for plant growth. The Aqua system showed no lettuce growth and experienced complete fish mortality. The fish-to-vegetable ratio used did not meet the nutritional demands of lettuce. Further studies are needed to determine an appropriate fish-to-vegetable ratio that provides sufficient nutrients to plants in aquaponics, along with the maintenance of optimal pH control.