Aquaponics is aquaculture and horticulture, combined.
99% of the phosphate in my system is through my fish feed, which may include:
Organic Rice Bran, Organic Canola Meal, Organic Whole Corn, Organic Alfalfa Meal, Organic Linseed Meal, Dicalcium Phosphate, Calcium Carbonate, Choline Chloride...