How big does Koi get?

Koi reaches an adult standard length of 50–90 cm (excluding the caudal fin). Size the tank for that, not for the juvenile you bring home — the difference is often several times over, and upgrading later costs more than buying once.

What water does Koi need?

5–30 °C, pH 7–8.5, 5–20 dGH, 4–15 dKH. At 25 °C wide it is one of the more forgiving ranges.

What is the smallest tank for Koi?

At least 3000 L, and no shorter than 200 cm. That is the floor for long-term keeping, not for short-term survival: volume buys water stability and length buys swimming room, and neither substitutes for the other. It is not a schooling fish, so a single specimen or a pair is fine.

What is Koi like to keep?

Temperament: peaceful. Difficulty: beginner. It occupies the all levels and is omnivore. With plants it is "Eats plants".

Can Koi be kept with its most common tank mate?

The checker returns "Not recommended together". Koi and Goldfish is a recorded conflict in this atlas. Predation, territorial fighting or conspecific aggression is the usual outcome, and a bigger tank does not change it.

G-01 / 32Freshwater

Koi锦鲤

Cyprinus carpio · Cyprinidae

A pond carp reaching 60-90 cm that no indoor aquarium can properly house.

Illustration to come

G-01 / 32 · Koi Cyprinus carpio

SpecificationsFish atlas

Name: 锦鲤
Scientific name: Cyprinus carpio
Family: Cyprinidae
Origin: Japan (bred from carp introduced from China)
Adult size: 50–90 cm
Temperament: Peaceful
Diet: Omnivore
Water level: All levels
Level: Beginner
Min. tank: 3000 L
Min. length: 200 cm
Plant safe: Eats plants

Water requirementsFreshwater

Temp.5–30 °C

pH7–8.5

Hardness5–20 dGH

Alkalinity4–15 dKH

Units: temperature in °C, hardness in German degrees (dGH / dKH), marine salinity as specific gravity at 25 °C, volume in litres. These are the values recorded for the species and do not follow the site unit switcher.

Keeping notes

1A pond fish at 60-90 cm; no indoor tank gives it the volume and swimming length it needs.
2Budget over 1000 L per adult and a pond at least 1.2 m deep for safe overwintering.
3Survives 5-30 °C, but feed only above 10 °C and stop entirely during cold spells.
4Omnivorous and greedy: it strips pond plants and stirs the bottom, demanding strong filtration and aeration.
5Aggressive at feeding time and a poor match for slow fancy goldfish.

Check a tank mate

Jump straight to the verdict for Koi against this one — no need to pick it again.

Recorded conflictGoldfishCarassius auratus→

Frequently asked questions

How big does Koi get?: Koi reaches an adult standard length of 50–90 cm (excluding the caudal fin). Size the tank for that, not for the juvenile you bring home — the difference is often several times over, and upgrading later costs more than buying once.
What water does Koi need?: 5–30 °C, pH 7–8.5, 5–20 dGH, 4–15 dKH. At 25 °C wide it is one of the more forgiving ranges.
What is the smallest tank for Koi?: At least 3000 L, and no shorter than 200 cm. That is the floor for long-term keeping, not for short-term survival: volume buys water stability and length buys swimming room, and neither substitutes for the other. It is not a schooling fish, so a single specimen or a pair is fine.
What is Koi like to keep?: Temperament: peaceful. Difficulty: beginner. It occupies the all levels and is omnivore. With plants it is "Eats plants".
Can Koi be kept with its most common tank mate?: The checker returns "Not recommended together". Koi and Goldfish is a recorded conflict in this atlas. Predation, territorial fighting or conspecific aggression is the usual outcome, and a bigger tank does not change it.