Three similar and independent aquaponics systems, each consisting of a pond (VEf = 1.5 m3) and three hydroponic beds (HB) with 0.270 m3 total volume and 0.9 m2 total crops area. In each HB 0.076 m3, volume of river stone were used as substrate (1″ particle-size, previously washed and disinfected, NaClO 5%) and a volume of 0.104 m3 of water, to give a total of 0.180 m3 VEf (Fig. 1).