Aquarium species profile

Koi

Cyprinus rubrofuscus (domesticated) · Captive-bred (originally from East Asia — China, Japan)

Minimum tank1,000 gal pond

Adult size24–36"

Care levelModerate

TemperamentPeaceful

Temperature35–77°F

pH range6.8–8.2

Diet

Omnivore – quality Koi pellets, wheat germ pellets (winter), vegetables, insects, earthworms

Compatible tank mates

Other Koi, large goldfish (Shubunkin, Comet), Golden Orfe; pond fish only

Tank mates to avoid

Small fish (will eat or outcompete), tropical fish, indoor aquariums

Care notes

Koi are pond fish — not suitable for indoor aquariums at adult size. Among the most popular ornamental fish worldwide. Hundreds of recognized varieties (Kohaku, Sanke, Showa, etc.). Live 25–35+ years; some over 200 years recorded. Extremely social and trainable. Water quality is critical — large bioload.

Check the whole aquarium. Tank size alone does not establish compatibility. Confirm adult size, water overlap, social grouping, territory, diet, and the individual animals before stocking.

Check compatibility in Fishician