Goldfish in a nano

Save the Little Fish demo · Nano, 5–10 gal · calm, like a pond or swamp · running 345 days · shared October 2026

Goldfish grow to 20 cm or more and make a lot of waste. A nano tank is a short-term home at best.

Needs changes

The fish

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Goldfish · Carassius

Carassius auratus

Domesticated in China from wild carp · pond

Photo: IssamBarhoumi, CC BY-SA 4.0

× 2

Already too big for this tank.

Shared range 10–24°C
Every species is comfortable in this range.
Goldfish outgrows this tank
It reaches about 20 cm. A rough rule is a tank at least 4 times the fish’s length, so 80 cm or more.
Overstocked (480%)
Too much waste for the water. Remove fish, pick a bigger tank, or plan on heavy filtration and large water changes.
Tank size is a guess
Size and stocking checks use a typical tank of the size you picked. Add the real length and volume for a sharper answer.
Some values are estimates
Care data for Goldfish is estimated or taken from the genus, not yet checked against a source.