Dissolved oxygen mostly remained between 6 and 7 mg·L− 1 in the low water exchange recirculation system (R) for both dietary treatments (6.54 ± 0.29 mg·L− 1 and 6.66 ± 0.44 mg·L− 1 respectively for the treatments RL and RC), while it fluctuated between 4 and 6 mg·L− 1 in the flow-through water system (F) for both dietary treatments (5.41 ± 0.76 mg·L− 1 and 5.40 ± 0.55 mg·L− 1 respectively for the treatments FL and FC) (Table 1).