water (about 500 L/h) and continuous aeration to maintain the dissolved
oxygen level at above 5 mg/L. Approximately 30% of the water
in each tank was replenished twice daily. Fish were fed with the experimental
diets three times daily (08:30, 12:30, and 16:40). Care was
taken to ensure that no uneaten food remained in the aquaria during
feeding. The amount of feed consumed by the fish in each aquarium
was recorded once a week. Fecal matter was also quickly removed during
the experiment. During the experimental period, samples of water
were collected 10 min before and after feeding once a week; temperature
ranged from 26 °C to 32 °C, dissolved oxygen ≥ 5.0 mg/L,
pH 7.2 ± 0.20, and total ammonia–nitrogen 0.055 ± 0.012 mg/L. The
Zn concentration in rearingwater ranged from1.4 to 1.7 μg Zn/L. The experiment
was conducted at ambient temperature and subjected to natural
photoperiod. Fish were bulk weighed every 2 weeks, and aquaria
were thoroughly cleaned when the fish were removed for weighing.
Mortality was checked daily.