The feeding trial was conducted in an indoor recirculation system, the system contained 24 fibreglass tanks with cylindroconical bottoms (diameter: 80 cm, water volume: 300 L). Each tank was connected to a filter tank filled with
zeolite and activated carbon. Water was recirculated through the filter at a rate of 4 L min−1. During the experiment water temperature ranged from 27 to 32 °C (mean 29.3 °C), pH= 7.5, NH4 + -Nb0.1 mg L−1. Aeration was supplied to each tank 24 h day−1, dissolved oxygen was maintained 5.5 mg L−1 and photoperiod was 12D:12L with the light period from 07:30 to 19:30 h.