Ranchu Goldfish
Carassius auratus
Cyprinidae
FishDifficulty: ●●●●○Data: well-established
About
The ranchu is the dorsal-less, hooded fancy goldfish the Japanese call the king of goldfish: an arched back, a short twin tail tucked under at a sharp angle, and a wen that takes a year or more to develop. Mature fish reach 15-20 cm and are heavy, broad-bodied animals, however small they look in a shop tank. Bred to be viewed from above in shallow vats, it swims slowly and cannot compete with single-tail goldfish for food, while its own heavy waste ruins the pristine water it depends on.
Care
Give one ranchu at least 120 L over a 90 cm footprint, keep the flow gentle and change at least half the water weekly. Feed pre-soaked sinking pellets twice a day, and never house it with fast single-tail goldfish.
Diet
Omnivore that grazes plants and algae; feed small portions twice daily. Pre-soak dry food, because swallowed air and swelling pellets are a common cause of the buoyancy problems short-bodied fancies suffer from.
Tankmate compatibility
Possible with care (38)
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Avoid (233)
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Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
What works for this species, most reliable first.
- Breeding tuberclesStrong · only in breeding condition — they vanish out of season
Goldfish and their cyprinid relatives grow small white bumps on the gill covers and leading pectoral rays when they come into breeding condition.
Frequently asked questions
- What tank size does a Ranchu Goldfish need?
- A Ranchu Goldfish needs an aquarium of at least 150 litres (39.6 US gallons) with a footprint at least 110 cm (43.3 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Ranchu Goldfish need?
- Ranchu Goldfish does best at 10–25 °C (50–77 °F), pH 6–8 and a general hardness of 6–25 °dGH.
- What group size does a Ranchu Goldfish need?
- Ranchu Goldfish is a social species — keep a group of at least 2 so natural behaviour emerges and stress stays low.
- Is the Ranchu Goldfish suitable for beginners?
- Ranchu Goldfish is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.
Sources
Water & tank
Temperature10–25°C
Optimal temp.16–21°C
pH6–8
Hardness (GH)6–25°d
Carbonate (KH)4–15°d
Adult size20 cm
Min. volume≥ 150 L
Min. tank length≥ 110 cm
Group size≥ 2
Swimming zoneAll levels
TemperamentPeaceful
Water typeFreshwater
FlowLow
Lifespan~10 yrs
Try in the calculator