Nine things you didn’t know about goldfish

  1. Whereas Koi need deep water to develop properly, typically 120cm, fancy goldfish need shallow water in order to produce their fleshy head growths to their maximum potential. Even adult Japanese ranchu are not kept in more than 20cm water depth.
  2. Goldfish are easy to sex. Males develop white spots on their gill covers called tubercles, or breeding stars, and white ridges on their pectoral fins. Females are often lopsided when viewed from above, and they’re ready to spawn, their bellies are very soft to the touch. 
  3. There are many types of raspberry-like head growths on fancy goldfish, and they are named after animals, depending on the shape. The oranda or ranchu breeder may be able to recognise buffalo head and tiger head, as well as the well-known lion head. Then there is the goose head, and even the frog and toad head!
  4. The heaviest goldfish on record were both caught in the UK, and by school children. A 5 lb specimen was caught by Nick Richards in 2010, which was then topped by 4oz in 2017 by 10-year-old schoolgirl Lois Chilvers. Both were caught in lakes and were probably released (illegally) as unwanted pets.
  5. A wild type bronze goldfish, (Carassius auratus,) and the Crucian carp (Carassius carassius,) can be told apart by two distinguishing features. Juvenile Crucians have a black spot at the base of the tail, and the dorsal fin on Crucian carp is convex, whereas the dorsal fin on goldfish is concave. 
  6. Goldfish varieties may be named different things, depending on if they are being kept in China or Japan. Telescope eyes are Dragon eyes in China, but named Demekin in Japan. And Orandas, Azuma nishiki. Pearlscales are named Hama nishiki in Japan, and Pompons are called Hanafusa.
  7. A goldfish with a mix of metallic scales and transparent scales is known as Nacreous, whereas a fish with no metallic scales is called matte. Red and white fish with matte scales are called Sakura, after the Japanese cherry blossom. In koi carp, fish with glittering scales are called Ginrin, and naked, scaleless fish, like wild leather and mirror carp are called Doitsu, pronounced Doits.
  8. Goldfish have been kept for their aesthetic values for over 1000 years. In the Chinese Sung Dynasty golden fish were kept in the vicinity of temples before spreading to Korea and Japan by 1500 AD. By 1600 they had made it to Europe and were considered widespread by as early as 1800. The nineteenth-century also saw their introduction to America. 
  9. In his 1917 book titled Goldfish Varieties and Tropical Aquarium Fishes, William T.Innes, who the Neon tetra is named in honour of, was already writing about the perils of the goldfish bowl, and stating that “the small globe is indeed an abomination.” 100 years on, goldfish bowls are still sold today.


Jeremy Gay

Author of three fishkeeping books and lifelong fishkeeper. Experience includes editor of Practical Fishkeeping magazine, editor of Pet Product Marketing magazine, multi award- winning livestock manager and aquatic store manager.