Ryukin Goldfish – Carassius auratus
Species name: Carassius auratus
Common names: Ryukin Goldfish
Family: Cyprinidae
Order: Cypriniformes
Class: Actinopterygii (ray-finned fishes)
Maximum length: 12 in (30 cm).
Minimum tank size: 50 gallon for an adult specimen
Hardiness: Easy
Aggressiveness: May nip at fins. Will eat fish that can fit in it’s mouth.
Distribution: Central Asia, China, Japan
Diet: Omnivore. In the wild, they feed on a wide range of food including plants, small crustaceans, insects, and detritus.
In captivity, they will accept most aquarium food including pellets, flakes, and live prey such as worms.
Additional information:
Often referred to as the Japanese ribbon-tail, the fringe-tail or the veil-tail, the ryukin goldfish is a stunning creature. A member of Cyprinidae family, which includes all the ‘fancy goldfish,’ its sheer presence has captivated fish-fanciers for centuries. It’s thought to have arrived in Japan around 1770 via the Ryukyu Islands (from where it gets its name), which lie between Japan and Taiwan and early Japanese texts name the fish the onaga (long-tail), or the nagasaki goldfish.
The ryukin goldfish is strikingly similar to the fan-tail but its most distinctive feature, a large hump just behind the head which develops as the fish matures, makes the ryukin easily identifiable. It has an unusually deep (almost as deep as it is long), egg-shaped body and a high dorsal fin which gives the fish a somewhat elevated appearance. The ryukin has a wide tail which typically has two lobes but fish with three or four lobed tails are not uncommon. They are normally red, white or a combination of the two in color. Nevertheless, there is a calico variant of the species which has a blue base color, a mixture of speckled
pigments and the occasional metallic scale on its flanks.
As with most goldfish differentiating between the sexes in ryukins is practically impossible until they have reached sexual maturity. Ryukin goldfish become sexually mature when they measure 4 inches/10 centimeters in length and are best sexed during the spring or early summer – the breeding season. Males will grow white spots or tubercles on their gill covers and heads and, due to carrying eggs, females will become fat. The tubercles displayed by male fish during the breeding season can resemble the fish parasite Ichthyophthirius multifilliis commonly known as white-spot. However, spotting the difference is relatively uncomplicated because, unlike white-spot, they don’t cover the fish’s body.
The Ryukin goldfish is extremely hardy and is an ideal fish for novice aquarists but in spite of this there are a few guidelines which should be followed. As the ryukin is a round-bodied fish it is prone to suffer from swim-bladder difficulties. When choosing a ryukin goldfish always go to a reputable fish stockist and pick a fish that isn’t showing any signs of swim-bladder problems. Symptoms of swim-bladder difficulties include a fish standing on its head or floating motionless in the water. A healthy ryukin can easily push the water aside as it makes its way through the aquarium.
A reasonably active, strong swimming fish the ryukin can be housed with most other types of goldfish including the lion-head, the oranda and the ranchu. But it should not be kept with weaker species such as the telescope-eye goldfish or the bubble-eye goldfish which will struggle to compete for food with the ryukin.
Mature ryukin’s can grow up to 12 inches/30 centimeters in length and as a result a fairly hefty tank with a minimum volume capacity of around 100 – 120 liters is required to adequately house the fish. No more than four ryukin goldfish should be kept in a tank this size. They will thrive best in water with a temperature of 20 – 24°C (degrees Celsius), and a pH value between 7 – 8. Also, the ryukin goldfish produces an excessive amount of ammonia and other waste material. Regular water changes, once every two weeks, are needed to prevent the aquarium becoming polluted. And always ensure the nitrate level in the aquarium never exceeds 20 ppm (parts per million), as higher levels will damage the fish’s swim-bladder.
Finally, the ryukin goldfish has a good appetite and enjoys a variety of foods. It will readily eat bloodworm, daphnia and any aquatic plants that the aquarium is home to. But due to its tendency to suffer from swim-bladder problems floating fish-flakes should be avoided as too many of these can lead to bloating. Goldfish pellets are fine but be sure to soak them in water before feeding them to the fish so that they can be easily digested.
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