.3. Results3.1. Water quality and ORP control During the experimental period, the ORP of RAS-O3was main-tained within the range 300–320 mV. By adjusting the injection of pure O2, the oxygen saturations of RAS-C and RAS-O3were main-tained at about 110% at the outlets of the fish tanks to exclude the possibility of increased oxygen concentration being caused by the ozonation of RAS-O3.There were no significant differences between RAS-C and RAS-O3in any of the measured water parameters TAN, TSS, NO2-N, andPO4-P (Table 1). The TRO of RAS-O3was below the detection limit(0.02 mg L−1) during the whole period.