The reason why goldfish are not as good as Rhodeus sinensis is because Rhodeus sinensis is not picky about water temperature and quality, and has a strong adaptive ability. As long as the water contains enough oxygen, it doesn't matter if it's dirty, whereas the goldfish is not picky about water temperature and quality, and has a strong adaptive ability. Grass goldfish, also known as golden carp, is a kind of ornamental fish, is the ancestor of goldfish, the earliest documented is the Warring States period. Rhodeus sinensis is the common name for the fish belonging to the carp subfamily Carpaceae (Rhodeus sinensis subfamily) of the order Carp, also known as the four-square skin, mirror fish, color round er, for a group of small freshwater fish.