Ryukin

The ryukin is a selectively bred form of goldfish with a characteristic egg-shaped, swollen body. Its hallmark is a high dorsal hump beginning just behind the head. The dorsal fin is tall and stands vertically. The tail fin is split, often long and flowing, with an angle of about 90 degrees between the lobes. Colour ranges from solid red, white, or black to variegated calico patterns. Adult fish can reach 15–20 cm in length. Sex differences become apparent during spawning: males become slimmer, and small white tubercles appear on their gill covers and pectoral fins.

This is an artificially created selectively bred form and does not occur in nature. The ancestors of goldfish come from waters in China, Korea, and Japan. In the wild, their feral relatives inhabit still or slow-moving freshwater bodies with silty bottoms and abundant vegetation.

Ryukins have a calm and peaceful temperament. They are fairly active, but because of their body shape they swim more slowly than many other fish. They are compatible with other peaceful species, though it is preferable to keep them in a species tank or with other goldfish varieties. When housed with active or aggressive tank mates, there is a risk of damage to their long fins.

A spacious tank of at least 75 litres per individual is required, as these fish create a high bioload. Powerful filtration and regular water changes are essential. Optimal temperature is 18–22 °C, water pH 6.0–8.0, water dH 5–19. The substrate should be smooth with no sharp edges to prevent injury to fins and body. Plants should have firm leaves, as the fish may nibble them.

Ryukins are omnivorous and voracious. The diet should include both animal and plant components. Specialized dry foods for goldfish are recommended, supplemented with plant matter such as blanched lettuce or spinach. Feed small portions several times a day, avoiding overfeeding, which often leads to digestive problems and swim bladder issues.

Fish reach breeding age at around two years. A separate tank of 50–80 litres with fine-leaved plants or specialized spawning substrates is used for spawning. An increase in temperature of 3–5 degrees and the addition of fresh soft water serve as triggers. Usually two to three males are placed with one female. After spawning, remove the adults to prevent them from eating the eggs.

Ryukins are prone to diseases caused by poor water quality, overstocking, and improper feeding. Swim bladder disorders, fin rot, whitespot, and fungal infections are common. Prevention includes maintaining clean conditions, quality filtration, monitoring water parameters, and proper feeding schedules. If signs of disease appear (lethargy, coating, body deformity), isolate the fish in a quarantine tank.

When selecting a fish, pay attention to its activity: a healthy specimen should be mobile with clean fins showing no signs of deterioration or coating. Eyes should be clear without cloudiness. Avoid fish with a deformed spine, signs of wasting, or an unusually swollen belly if unrelated to overfeeding. Observe the fish's behaviour in the shop to ensure there is no lethargy or coordination problems.