One species · 5 varieties
Koi
Cyprinus rubrofuscus
Also known as Nishikigoi, Cyprinus carpio, Japanese koi, Amur carp, Ornamental carp
FreshwaterFish
Care at a glance
- Temperature
- 39–81°F
- 4–27°C
- pH
- 7.0–8.5
- Adult size
- 23.6 in
- 60 cm
- Minimum tank
- 264 gal
- 1,000 L
- Temperament
- Peaceful
- Social behavior
- Social
- Tankmates
- With caution
- Swim level
- Bottom
- Diet
- Omnivore
- Difficulty
- Medium
- Breeding
- Medium
- Rarity
- Very common
- Family
- Cyprinidae
- Origin
- Ornamental form of the Amur carp from East Asia, now kept in garden ponds worldwide after centuries of color breeding in Japan and China.
Pick a variety
One setup covers every line on this page: care is the species' care.
Overview
Koi are big, peaceful pond fish that spend most of their time near the bottom. They are best kept by someone with a little experience.
Did you know
Koi learn to recognize the people who feed them and will take food from the hand. Some ponds have held the same fish for more than 50 years.
Caring for the koi
Koi are pond fish, not aquarium fish. A single koi needs at least 264 gal (1,000 L) to start, and a group needs a pond of several thousand liters. They are big, messy eaters, so give them strong filtration.
Koi handle a very wide temperature swing, from 39 to 81°F (4 to 27°C), with a pH of 7.0 to 8.5. They stay active in summer warmth and slow to near dormancy under winter ice. Stable, well oxygenated, well filtered water matters far more than a narrow parameter target.
Feed a varied omnivore diet of sinking koi pellets and greens, with occasional live or frozen foods. Keep koi in groups. They are peaceful and mix well with goldfish and other large, peaceful pond fish. They uproot plants and eat anything small enough to swallow.
Good to know
Koi are usually sold under the old name Cyprinus carpio, but the ornamental strains trace to Cyprinus rubrofuscus, the Amur carp. Koi are also known as nishikigoi. Color breeding began in Japan in the 1800s and now covers dozens of named varieties, such as Kohaku, Sanke and Showa. A koi can live for several decades.
In the wild
The wild Amur carp is a hardy river and pond fish from East Asia. It lives in slow rivers, lakes and flooded fields, rooting through soft bottoms for food.
Other named lines
Koi classes are Japanese pattern names for the same carp, and these two are the blue-backed classes.
- Asagi
- blue net-pattern back, red-orange belly
- Shusui
- scaleless asagi with a single dorsal scale row
Common questions
What size tank does a koi need?
A koi needs at least 264 gal (1,000 L). It spends most of its time in the bottom.
What temperature and pH does a koi need?
A koi is comfortable at 39–81°F (4–27°C) with a pH of 7.0–8.5.
What does a koi eat?
A koi eats a varied omnivore diet of sinking koi pellets and greens. Give it occasional live or frozen foods as well.
How big does a koi get?
An adult koi reaches about 23.6 in (60 cm).
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