A 42-d feeding experiment was carried out in the experimental hatchery
of the College of Aquaculture and Fisheries, Can Tho University, Vietnam.
The experiment was set up as a completely randomized design with three
replicates per treatment in 100-L plastic tanks containing 80 L of slightly
brackish water (salinity = 5 ppt) provided with soft continuous aeration.
Water temperature varied between 27 and 28.9◦C over the experimental
period. Juvenile monosex male Nile tilapia were purchased from a reliable
provider in Bac Lieu province and visually checked for signs of disease and
parasites. Before starting the experiment, fish were held in a 1 m3 tank for
1 week for acclimation to laboratory conditions and feeding method (on a
feeding tray for the dual purpose of measuring feed consumption and reducing
water-quality issues). After acclimation, 50 uniformly sized monosex male
Nile tilapia juveniles of individual weight 0.33 ± 0.06 g were stocked in each
tank. Fish were fed twice a day at 7:00 and 17:00 h to satiation. About 1.5 h
after feeding, unconsumed feed was removed carefully by siphoning, transferred
to aluminium cups, and dried to a constant weight. Every day, about
30% of the volume of the water of each tank was exchanged.
Fresh GW was collected in Bac Lieu province, Vietnam, and cleaned
with 5 g L−1 saline, air-dried, and ground into ∼500 μm particles. Kien
Giang fishmeal was purchased from CATACO Company, Can Tho. Other
ingredients such as soybean meal, rice bran, squid oil, gelatine, and wheat
flour were purchased from commercial suppliers. The dietary ingredients
were analyzed for their proximate composition prior to the formulation of