Integration of aquaponics into a flow-through fish culture system improves water quality

Aquaponics, the integrated culture of fish and plants, can improve effluent water quality through reductions in suspended solids and nutrient concentrations.  Fish culture operations increase nutrient and suspended solid concentrations while plants growing in the effluent filter suspended solids and remove nutrients to sustain growth.  The integration of aquaponics into recirculating fish culture systems is well developed but little information exists for flow-through culturing systems.  Variability in initial water chemistry and temperature for flow-through systems has made extrapolation from recirculating systems to flow-through systems difficult.  Water temperature is of critical importance.  Warm season crops grown in effluent with a constant temperature of 13°C either failed to germinate or grew very poorly in both spring and summer despite warm air temperatures.  Cool season crops on the other hand, grew well in all seasons despite high air temperatures during the summer.  Nutrient removal capability varied with plant species.  Kohlrabi removed an average of 25% of ammonia while lettuce and watercress averaged 18% and 9% respectively.  Kohlrabi, lettuce, and watercress removed an average of 22%, 2%, and 9% respectively of nitrate.   Phosphate removal averaged 2-7%.  Careful selection of plant species to grow aquaponically can lead to significant reductions in effluent nutrient concentrations.