Ranchu

Looks how to spot one

Scaled, egg-shaped, dorsal-less twin-tailed fancy goldfish with head growth (wen)

A chunky, egg-shaped goldfish with a deep belly, a strongly arched back and no dorsal fin at all. The broad tail root curves sharply down so that the short double tail is tucked in at about 45 degrees. A raspberry-like hood (wen) slowly builds up over the head, taking a year or more to show on young fish.13

Personality what they are like

A peaceful, easygoing fish. Without a dorsal fin it swims more slowly than ordinary goldfish, so it is happiest alongside other gentle, round-bodied fancies rather than quick single-tailed goldfish.14

Daily activity how busy a day looks

Low to moderate. A slow, waddling swimmer that likes open, shallow-to-medium depth swimming space rather than strong currents.15

Grooming and care the hands-on bits

Needs a good filter, regular partial water changes with dechlorinated, temperature-matched water, and routine tests showing zero ammonia and nitrite. Keep feeding moderate and use smooth decor so the soft head growth stays tidy.54

Home where they are happiest

Keep in a filtered aquarium, not a bowl. Aqueon suggests at least 40 litres (10 US gallons) per adult fancy goldfish, while the RSPCA advises at least 60 litres per goldfish, with wider tanks giving more stable water. Fancy goldfish are comfortable at about 20-23 °C (Aqueon gives 68-74 °F), and the RSPCA notes goldfish in general live at 10-21 °C without a heater. A pH of roughly 6.0-8.4 is fine (FishBase gives 6.0-8.0, Aqueon 7.0-8.4).456

Food basics what goes in the bowl

Omnivore. Offer a goldfish flake, granule or sinking pellet once or twice a day, only as much as is eaten in two to three minutes, with frozen or live foods as occasional treats.46

Company who they like around

Sociable and best kept in a group; FishBase suggests goldfish in groups of five or more. Good companions are other slow fancy goldfish such as lionheads and orandas.64

The story where it all began

Goldfish without a dorsal fin, known as egg-fish, have been bred for around 700 years, and dorsal-less lionheads were kept in China and Japan before the 1600s. Japanese breeders used these Chinese lionheads to develop the ranchu, refining a more arched back and a tucked-down tail, and it became Japan's most prestigious show goldfish.12

Recognised by the official bits

Japanese, Thai, American and British goldfish societies

Judged against show standards that look at the fish from above and from the side; Japanese standards are the strictest, and in Japan ranchu are shown in shallow bowls viewed from above1

Taxonomy

Dorsal-less, twin-tailed fancy variety of the domestic goldfish3

IUCN Red List

The parent species Carassius auratus is assessed as Least Concern6