2.2. Aquaria experiment
There were four replicate aquaria per treatment. Each aquarium (305030 cm)
was stocked with 12 O. aureus fingerlings weighing between 5 and 8 g (7.12F0.78
(meanFSE)). Fish were fed to apparent satiation three times daily (9:00, 13:00 and 17:00
h) for 8 weeks. At the beginning and at the end of the experiment, samples of fish were
taken for body composition analysis. Water quality was checked at the common outflow of
aquaria in the recirculation system. Water temperature and dissolved oxygen were
measured twice daily (8:00 and 17:00 h). Levels of pH, nitrite and total ammonium were
measured weekly. When necessary, by addition of tap water into the system (adjusting
water flow), nitrite and total ammonia levels were maintained below 0.15 and 2.5 ppm,
respectively, and dissolved oxygen above 3.5 ppm. The photoperiod was kept at 13 h
day 1 (from 6:00 to 19:00 h).