Experimental design
A group of 1050 male goldfish measuring 51.20 ` 2.21 g and 14.22 ` 1.37 cm was used for the broodstock–conditioning experiment with the carotenoid-enriched diet. The experiment lasted for 150 days, and it compared the diets enriched with synthetic astaxanthin (Carophyll Pink 10%; DSM Nutritional Products Philippines, Inc.dBright Science, Brighter Living, the Netherlands) and b-carotene (b-caro- tene 10% CWS; Direct Food Ingredients Ltd., England) with a control diet for a total of seven treatments run in triplicate.
For the fish-conditioning experiment, 21 circular fiber- glass tanks (3.77 m3; 2 m in diameter and 1.2 m in height) were used. The freshwater parameters of temperature, pH, dissolved oxygen, nitrite, and ammonia were measured daily during the experimental period.
One month before the end of the experiment, a group of 300 female broodstock of 6-month-old goldfish (47.21 ` 2.19 g) from a commercial hatchery was matured for 30 days in a fiberglass tank (2 m3) with the control diet to achieve egg fertilization. The freshwater parameters of temperature, pH, dissolved oxygen, nitrite, and ammonia were measured daily during the 30 days of female maturation.