Common goldfish

Long body, a single short tail and a smooth head

A metallic domestic goldfish form. Its tail is shorter and less deeply forked than a comet’s; unlike a fantail it has an elongated body and a single caudal fin. Dark juvenile colour does not identify a separate species.

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.

Active larger fish can outcompete small, slower double-tailed forms. Cold tolerance does not make an unfiltered bowl suitable. Swimming and feeding ability vary among forms. Provide filtration, oxygenation and maintenance.