Fantail domestic goldfish — left-facing AI-generated side-view illustration

Fantail goldfish

Carassius auratus

Rounded body, ordinary eyes and a divided fan-shaped tail

Look for a short rounded body, normal eyes, a smooth head and a divided double tail. Unlike an oranda it has no developed headgrowth; unlike a ranchu it retains a dorsal fin. A double tail alone does not identify a fantail.

Adult length: About 10 cm
Lifespan: Up to 30 years
pH: 7–8.4
Hardness: 5–19 dGH

Natural habitat: Wild habitats include rivers, lakes, ponds and ditches, often in vegetated still or slow water; ornamental goldfish are domesticated forms.

Match companions to actual swimming and feeding ability. A compact body does not justify a small bowl. Plants may be eaten or uprooted. Swimming and feeding ability vary among forms. A shared species name or overlapping temperatures does not establish compatibility. Provide filtration, oxygenation and maintenance.

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Appearance and identification

A fantail has a dorsal fin but no headgrowth; an oranda develops headgrowth and a ranchu lacks the dorsal fin.

Same-species behaviour

Assess individual swimming and feeding; a group size suitable for every form remains unknown.

Space requirements

A dimensioned adult housing plan remains unverified. Avoid small, unfiltered containers.

Diet and feeding

Use an appropriate goldfish diet with suitable varied foods, adjusting to condition and water quality.

Compatibility limits

Active single-tailed fish may outcompete slower double-tailed forms. Avoid fin nippers and overly competitive companions.

Aquarium environment

Goldfish may eat or uproot plants; aquarium illustrations do not establish plant safety.

Sources