Ranchu Goldfish (Carassius auratus var. Ranchu) Care Guide
Considered the king of goldfish in Japan, the Ranchu has no dorsal fin, a deeply curved back, and a prominent wen (head growth). Slow swimmers that require smooth decorations to avoid injury.
Compiled by Aquairi from published sources · Published · Updated
Overview
Carassius auratus var. Ranchu is a species in the family Cyprinidae. Considered the king of goldfish in Japan, the Ranchu has no dorsal fin, a deeply curved back, and a prominent wen (head growth). Slow swimmers that require smooth decorations to avoid injury. Highly prized in competitive goldfish shows.
Taxonomy
- Family: Cyprinidae
- Genus: Carassius
- Scientific name: Carassius auratus var. Ranchu
- Other names: Buffalo Head Goldfish
- Origin: East Asia
Habitat
The ranchu is a dorsal-finless fancy goldfish (Carassius auratus) bred in Japan for a curved back and head growth. It descends from domesticated East Asian goldfish stock and, lacking a dorsal fin, is a slow swimmer best kept with similar fancy types.
Tank requirements
- Minimum tank volume: 150 L
- Temperature: 18-22 °C
- pH: 6.5-8
- GH: 5-20 °dGH
- Water flow: low
- Adult size: 12-20 cm
- Lifespan: 10-15 years
- Difficulty: intermediate
Diet
Classified as omnivore. Recommended feeding frequency: 2x daily. In captivity, offer a varied diet appropriate to the species — quality prepared foods supplemented with frozen or live items of suitable size.
Compatibility
- Temperament: peaceful
- Position in tank: middle
- Compatible tank mates: Another Goldfish, Dojo Loach, Nerite Snail
- Avoid with: Tropical Fish, Fast Swimmers, Fin Nippers
Breeding
- Breeding strategy: egg-scatterer
- Breeding difficulty: advanced
Ranchu Goldfish Breeding Guide
Overview
The Ranchu is a selectively bred variety of the goldfish, Carassius auratus, distinguished by the absence of a dorsal fin, a deeply curved back and a prominent head wen. It spawns with the same egg-scattering biology as other goldfish; the difficulty lies in producing offspring that show the smooth dorsal-less profile and well-formed wen prized in this variety.
Sexing
Mature goldfish are sexed most reliably in the breeding season, when males develop small white breeding tubercles (stars) on the gill covers and leading pectoral-fin rays. Gravid females become noticeably rounder and deeper-bodied. Tubercles are typically present from spring through autumn.
Conditioning
A breeding programme normally starts in early spring with the water warmed to about 17 degrees C (63 degrees F), with fish well reconditioned after the cooler winter. Breeders commonly spawn one female with two or three males, and add plenty of fine-leaved spawning medium such as hornwort or a spawning mop.
Spawning Behavior & Trigger
Spawning is triggered by a significant temperature rise in spring as the water approaches about 20 degrees C (68 degrees F). Males chase the gravid female and prompt her to release eggs by bumping and nudging. The adhesive eggs scatter and stick to plants such as Cabomba, Elodea or a spawning mop.
Egg & Fry Care
Because goldfish eat their own eggs, parents must be removed as soon as spawning is over (the eggs are adhesive and cannot easily be moved). The eggs hatch in about four days and the fry become free-swimming roughly 24 hours later, when feeding begins. Fry are an undistinguished metallic brown and may take a year before developing mature goldfish coloration.
Common Challenges
Producing show-quality Ranchu requires heavy culling: only fry developing the smooth dorsal-less back, correct curvature and an even wen are kept. Some highly selectively bred goldfish can no longer breed naturally due to their altered shape, so selecting healthy, vigorous breeders that still spawn reliably is part of maintaining the line.