Common goldfish

Carassius auratus

Also known as gold fish

FreshwaterFish

Common goldfish (Carassius auratus) — לינה אבוגוש · CC BY-SA 3.0

Care at a glance

Temperature: 39–82°F (4–28°C)
pH: 6.0–8.0
Adult size: 7.9 in (20 cm)
Minimum tank: 24 gal (90 L)
Temperament: Peaceful
Social behavior: Social
Swim level: Middle
Difficulty: Beginner
Breeding: Medium
Rarity: Very common
Origin: China
Family: Cyprinidae

Overview

Goldfish are social and do better with company, so keep two or more, and budget far more space than people expect, starting around 90 liters and scaling up per fish. They are heavy eaters and big waste producers, so a strong filter and regular water changes are the real work here. Feed a quality goldfish pellet with vegetables and the occasional frozen food, and skip warm-water tropical tankmates since goldfish prefer it cooler. They are peaceful but will eat anything small enough to fit in their mouth.

In the wild

The common goldfish is a domesticated fish descended from wild carp in China, not a fish you collect from the wild today. Its carp roots show in what it needs, namely lots of room, cool water, and heavy filtration to handle the mess it makes. It tolerates a huge temperature range, from near freezing up to about 28 C, which is why it does well in unheated tanks and ponds.

Good to know

Carassius auratus is in the family Cyprinidae, the carp and minnow family. A single-tail common goldfish reaches around 20 cm in a tank and can grow larger in a pond, and well-kept fish often live well past ten years. It is an egg scatterer that spreads eggs over plants and gives no parental care.

Did you know

They have no stomach and digest food more or less continuously, which is why little and often beats one big meal and why overfeeding fouls the water so fast. Floating dry food can also make them gulp air, so pre-soaking pellets helps cut down on swim bladder trouble.