Common Goldfish

Carassius auratus

Also known as: Single-tail goldfish, Feeder goldfish

Water Parameters

• Temperature: 10–24°C
• pH: 7–8.4
• Hardness (GH): 89–357 ppm (5–20 dGH)

Values above are general hardness (GH). For carbonate hardness (KH), the buffer that keeps pH stable, see the water parameters guide.

Care Summary

The plain, orange, single-tailed fish most people picture when they hear the word goldfish, and the hardy ancestor from which every fancy variety was bred. Commons are fast, powerful, cold-tolerant fish that reach 25 to 30cm and can live for decades, which is exactly why they are so often mis-sold: bought cheaply as a 'feeder' or a bowl fish, they need a pond or a very large, heavily-filtered aquarium to do well. Given that space, clean cool water, and the company of other single-tailed goldfish, they are among the most robust and rewarding of all aquarium fish, personable, long-lived, and genuinely interactive. In Australia's temperate south they thrive in outdoor ponds, but they must never be released, as feral goldfish are a serious pest in local rivers.

Tankmates

The starting point of the whole goldfish family: a fast, hardy, single-tailed fish that grows large and belongs with its own kind or in a pond, not in a community of tropical fish. The single most important rule is to keep single-tailed goldfish (commons, comets, shubunkins) together and never with the round-bodied fancy varieties, because the fast single-tails outcompete and stress the slow fancies at every meal. They are too large and too messy for the small nano fish and shrimp often suggested as tankmates, both of which are eventually eaten or simply outmuscled. In Australia they are best suited to an outdoor pond in temperate regions or a very large aquarium, and must never be released, as feral goldfish are a declared pest in local waterways.

Compatible with

• Comet Goldfish
• Shubunkin

Avoid keeping with

• Fantail Goldfish
• Ryukin
• Oranda
• Ranchu
• Bubble Eye
• Cherry Shrimp
• Betta
• Tropical Warm Water Species

Common Problems

• outgrowing bowls and small tanks (reaches 25-30cm)
• heavy bioload overwhelming weak filtration
• being kept with slow fancy goldfish it outcompetes
• stunting and early death in unsuitable setups

Sources: seriouslyfish.com, fishbase.org · Last updated: 2026-06-20