more than two
granules and less than 20 granules of food for each
fish. During 6:00-18:00 a.m. to p.m., fluorescent lamps
with light intensity of 2 000-15 000 lx were used,
simulating nature illumination. At night, between
18:00 p.m. and 6:00 a.m., no artificial light was
provided. During the experimental period, the water
in the aquarium was exchanged 1/5 each day, and the
excretions were siphoned off every day with minimal
disturbance to the feeding of the fish being tested.