What tank size does a Common Goldfish need?

A Common Goldfish needs an aquarium of at least 300 litres (79.3 US gallons) with a footprint at least 150 cm (59.1 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Common Goldfish need?

Common Goldfish does best at 4–28 °C (39.2–82.4 °F), pH 6–8 and a general hardness of 6–25 °dGH.

What group size does a Common Goldfish need?

Common Goldfish is a social species — keep a group of at least 3 so natural behaviour emerges and stress stays low.

Is the Common Goldfish suitable for beginners?

Common Goldfish sits in the middle of the difficulty scale — manageable for a careful beginner who has done the reading, but it has specific needs worth researching first.

Species library

Common Goldfish

Carassius auratus

Cyprinidae

FishDifficulty: ●●●○○Data: well-established

📷 James St. John · CC BY 2.0 · resized · Wikimedia Commons

Common Goldfish — Carassius auratus — 📷 James St. John · CC BY 2.0 · resized · Wikimedia Commons

About

The common goldfish is the original single-tailed form of Carassius auratus, a hardy coldwater cyprinid domesticated from wild carp in China over a thousand years ago. Streamlined and torpedo-shaped, it is a fast, powerful swimmer that can exceed 30 cm and live for well over a decade. Sociable and endlessly hungry, it forages constantly across every level of the tank and produces a very heavy bioload, so it needs a large volume, strong filtration and ideally a pond rather than a small aquarium or bowl.

Care

A large, long-lived coldwater fish, not a bowl pet. Give a single-tail a pond or a heavily filtered 190 L+ per fish, keep it unheated at 16–21 °C, and expect it to dig and uproot soft plants.

Diet

Opportunistic omnivore grazing plants, algae, detritus and small invertebrates; feed sinking gel or pellets plus blanched vegetables, but sparingly to limit its notorious waste production.

Tankmate compatibility

Possible with care (38)

Avoid (233)

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Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.

Telling males from females

What works for this species, most reliable first.

Breeding tuberclesStrong · only in breeding condition — they vanish out of season
Goldfish and their cyprinid relatives grow small white bumps on the gill covers and leading pectoral rays when they come into breeding condition.

All the methods, with diagrams

Frequently asked questions

What tank size does a Common Goldfish need?: A Common Goldfish needs an aquarium of at least 300 litres (79.3 US gallons) with a footprint at least 150 cm (59.1 in) long — for this species, swimming length matters as much as raw volume.
What water parameters does a Common Goldfish need?: Common Goldfish does best at 4–28 °C (39.2–82.4 °F), pH 6–8 and a general hardness of 6–25 °dGH.
What group size does a Common Goldfish need?: Common Goldfish is a social species — keep a group of at least 3 so natural behaviour emerges and stress stays low.
Is the Common Goldfish suitable for beginners?: Common Goldfish sits in the middle of the difficulty scale — manageable for a careful beginner who has done the reading, but it has specific needs worth researching first.

Sources

Water & tank

Temperature4–28°C

Optimal temp.16–21°C

pH6–8

Hardness (GH)6–25°d

Carbonate (KH)4–15°d

Adult size30 cm

Min. volume≥ 300 L

Min. tank length≥ 150 cm

Group size≥ 3

Swimming zoneAll levels

TemperamentPeaceful

Water typeFreshwater

FlowModerate

Lifespan~15 yrs

Try in the calculator