Common Goldfish (Carassius auratus)
Some authorities claim that it was due to the high mineral content of the water in some volcanic areas of China and Japan that the black pigment in some fishes was lost, leaving only a gold colour. From these fishes there have been developed many fancy breeds; over 120 different varieties are recorded, but the Common Goldfish is still the most popular and the cheapest of this group. It has a bright red-gold metallic appearance, is scaled, and should have a broad short head with a small mouth, bright eyes, and the back and belly gently arched. The dorsal fin starts on the peak of the back, and the stiff caudal fin is moderately forked; the rest of the fins are held stiffly.
There are other colours available, Yellow-gold varieties are known as Canaries, white ones are called Pearls, and spotted or blotched ones are referred to as Orioles. Goldfishes will grow to over 13cm (5in) long.