APPLING COUPLED AND DE-COUPLED AQUAPONICS TO BETTER                                 UTILIZE RAS WATER  

Using coupled and decoupled systems together to fully utilize the nutrient stream from RAS facilities.

Coupled Aquaponics - This is the aquaponics paradigm that has been in place the longest.  In this model, the fish crop is fed a high protein diet often or, in some cases continuously throughout the day to maximize conversion efficiency (the fish can be fed anywhere from 3-7% body weight per day depending on size and species).  Metabolism of the feed results copious production of fecal material and ammonia, which is the next management challenge. Since mineralization of some fecal material is essential for providing phosphorus and other non-nitrogen nutrients for the plants, removing all fecal material with traditional mechanical filtration is not advisable and has the potential to starve the plant crop of some nutrients. The downside to this strategy in the coupled aquaponics model is that a waste stream is still generated by trying to manage the fecal load in the system.   Coupled systems are very good with the uptake of nitrates. This waste can be de-watered with geotextiles or filter presses, used in vermiculture or sold as fertilizer for traditional soil based agriculture but is typically still flushed to waste.       

De-Coupled Aquaponics - In the de-coupled aquaponics model, the process train is essentially the same as described above with several notable exceptions.  All fecal material is filtered from the main system circulation with fine screen drum filters and the plant crop is "de-coupled" from the fish system circulation and runs on a separate parallel loop with its own dedicated treatment train.   This arrangement offers several benefits over the coupled aquaponic model but does require more space, more equipment and more sophistication.  The de-coupled aquaponic paradigm does away with the need to constantly adjust the fecal load in the system to maintain nutrient balance as the fish and plants grow and their waste generation and nutrient requirements change.  This eliminates the waste stream from the drum filter in the coupled model.  In addition, since all solid waste is utilized and is independent from the fish system, the nutrient stream to the plants can be varied in volume and concentration to optimize plant growth without impacting fish water quality.   The consumption of waste and water discharges from RAS.