We experimentally investigated effects of four concentrations (4, 6, 8, and 10%) each of dietary Spirulina and Chiorella, as well as four concentrations of dietary astaxanthin (40, 60, 80, and 100 ppm in Carophyll Pink), on the body color of red- and white-colored carp, Cyprinus carpio. The total carotenoid concentration in the skin tissue of the red parts of the carp fed dietary Spirulina, Chiorella, and astaxanthin increased up to the second week of the experiment but decreased thereafter. The redness value of the Spirulina-and Chiorella-treated fish decreased up to the sixth week of the experiment and increased thereafter. However, the redness value of the astaxanthin-treated fish consistently increased, beginning in the second week. Of the three agents tested, astaxanthin in Carophyll Pink was the most effective at enhancing the redness of both red- and white-colored carp. The redness value of the fish did not statistically differ among the various concentrations of astaxanthin. Therefore, dietary supplementation with 40ppm astaxanthin would be the most economical method for enhancing the redness of red- and white-colored carp fingerlings.