From my own research, the easiest way to incorporate another cycle, to bring aquaponics in line with a digester is to use the fish poop and viscera(guts) in the digester. Bioslurry(effluent) is then diluted and used to grow plants... NOW, that can be integrated to feed the fish, by growing duckweed in some of the diluted bioslurry. Would need additional tanks and I have no idea on capacity, BUT pressing duckweed yields vegetable oil, leaving a high protein pulp, which can be dried and fed to the fish, or just feed the duckweed to the fish, if you don't want to mess with the oil, to make biodiesel. IF you make biodiesel, the waste vegetable glycerine can be made into soap, as well as diluted to feed the digester.

Best video on Youtube (that I have seen) with integrating Aquaponics and a digester is "Green Society Aquaponics".

https://www.youtube.com/watch?v=Pyz55YHE_Is