Ranchu Goldfish Care Guide - Setup, Diet & Breeding

Ranchu Goldfish are a rounded, deep-bodied fancy goldfish recognised by their prominent head growth, known as a wen, and their complete lack of a dorsal fin. Their arched back, short body and flowing paired and caudal fins give them a compact, graceful appearance, while the wen develops gradually as they mature. They are available in many colour patterns, including red, orange, white, black, calico and combinations of these shades.

Despite their elaborate appearance, Ranchu Goldfish are generally peaceful, sociable fish. Their body shape and short fins make them slower and less agile swimmers than streamlined goldfish varieties, so they are often seen moving calmly through the lower and middle areas of the aquarium while searching for food.

The Ranchu is a Japanese fancy goldfish with a long history of selective breeding. Its head growth and curved back are prized features, and high-quality specimens are judged by body shape, tail carriage, balance and the even development of the wen.

In nature, the species from which all goldfish descend is a hardy freshwater carp associated with ponds, slow-moving waters and vegetated habitats. Ranchu themselves are not a wild form; their distinctive shape is entirely the result of generations of human selection.

Ranchu Goldfish are a selectively bred ornamental variety of the domesticated goldfish, Carassius auratus. Their development is associated with Japan, from Chinese lionhead-type goldfish imported and refined during the nineteenth century in Asia.

A single adult Ranchu Goldfish should have at least 120 litres, with roughly 50 litres added for each additional adult. A tank measuring about 90 cm long by 45 cm wide is a practical starting point because floor space and swimming length are more useful than a tall, narrow aquarium. Use smooth sand or rounded fine gravel, open swimming areas and sturdy, smooth decor without sharp edges that could damage the fins or wen. Hardy live plants may be used, although they can be uprooted or eaten; efficient filtration and good circulation are important, but the flow should not be excessively strong for this less streamlined variety.

Up to around 20 cm (8 in) in adult body length, although many aquarium specimens remain closer to 15–18 cm (6–7 in). Females are often slightly larger and fuller-bodied than males, particularly when carrying eggs.

Ranchu Goldfish are omnivores and do well on a varied diet based on a quality sinking goldfish pellet or soft gel food. Supplement this with blanched vegetables such as peas, spinach and courgette, along with occasional frozen or live foods including daphnia, bloodworm and brine shrimp. Sinking foods are preferable because they allow these bottom-oriented fish to feed naturally and reduce the amount of air swallowed at the surface. Offer modest portions and remove uneaten food promptly.

Ranchu Goldfish are best kept with other similarly gentle, slow-moving fancy goldfish such as Orandas, Fantails, Ryukins and Telescope Eyes, provided the individuals are comparable in size and swimming ability. White Cloud Mountain Minnows and other small tropical fish are poor choices because of the temperature difference and the risk of competition or fin-nipping. Avoid fast, boisterous goldfish, fin-nipping species and predatory tankmates, as Ranchu may struggle to compete for food or may be injured.

Ranchu Goldfish are egg scatterers that usually spawn when seasonal conditions encourage courtship. Provide well-conditioned adults with a spawning mop or dense, soft-leaved plants, and increase feeding with varied, protein-rich foods before spawning. The male follows and nudges the female, encouraging her to release adhesive eggs while he fertilises them. Remove the adults after spawning because they readily eat the eggs. Hatching generally takes several days, and the fry require very small foods before progressing to larger offerings.

Mature females are usually broader through the abdomen and have a rounder body profile, especially during the breeding season. Mature males are often slimmer and may develop small white breeding tubercles on the gill covers and leading edges of the pectoral fins; these tubercles should not be confused with disease.