If you want to go the whole aquaponic way you would need to go back to an organic cycle, the bigger the better because it will be more stable.
They will mainly produce N more anything else so maybe not the best only input for flower, but a couple a gold fish in a dark tank could be a nice boost in veg . You will need to feed them and study a bit of the N cycle. The goldfishes maybe be a consumables too .
As Sfrigon said if you want a water only cycle it is easier to go with a living soil... Less trouble