The rosy bitterling (Rhodeus ocellatus) is a small freshwater fish belonging to the family Cyprinidae (carp). Females are about 40-50 mm long and males are 50-80 mm. Their bodies are flat with an argent-colored luster. However, males change to a reddish (sometimes purple) color during the spawning season (March to September) which functions to attract females. This reddish color is similar to the color of a red rose, which is why it is called a rosy bitterling.