In the first experiment (Exp Ι), red sea bream (initial mean body weight, 29.0 ± 0.1 g) were randomly distributed into nine polyvinyl circular tanks of 150 L capacity at a density of 33 fish per tank and in the second experiment (Exp II) olive flounder (initial mean body weight,
24.5 ± 0.3 g) were randomly distributed into a similar rearing system at a density of 35 fish per tank. Triplicate groups of fish were fed one of the experimental diets to apparent satiation (twice a day, 08:00 and 18:00 h) for 12 and 9 weeks, in Exp Ι and Exp II, respectively. The
tanks were supplied with sand filtered seawater at a flow-rate of3 L min−1 and aeration to maintain enough dissolved oxygen. The photoperiod was maintained on a 12:12 h (light/dark) schedule. The average
water temperature during the trial was 22.0 ± 1.8 °C. Uneaten
feed was collected 20 min after feeding and reweighed to determine
feed intake. Growth of fish was measured every three weeks. Feeding
was stopped 24 h prior to weighing or blood sampling to minimize
stress on fish.