Can koi live with fancy goldfish?

Verdict

Yes, with care

Yes, with care. Koi and fancy goldfish can share a tank, but watch one thing. A grown koi may treat small fancy goldfish as food, especially at night.

Koi59–77°F · pH 7–8.5

Fancy goldfish65–74°F · pH 7–8

What to watch

Watch outA grown koi may treat small fancy goldfish as food, especially at night.

What works

Both are fine at 65–74°F.
pH 7–8 suits both.

Water side by side

The green band is the temperature range both can live in.

The green band is the pH both tolerate.

Size to scale

Adult length in an aquarium. A fish can swallow anything that fits in its mouth, roughly a third to half its own length for predators.

Care at a glance

	Koi	Fancy goldfish
Temperature	59–77 °F	65–74 °F
pH	7–8.5	7–8
Adult size	24.0 in	6.0 in
Minimum tank	Pond	30 gal
Temperament	Peaceful	Peaceful
Swims at	All levels	All levels
Group	Groups of 3+	Alone or in pairs
Diet	Omnivore	Omnivore

Better tank mates for koi

All koi tank mates

Better tank mates for fancy goldfish

All fancy goldfish tank mates

Questions

Can koi live with fancy goldfish?

Yes, with care. Koi and fancy goldfish can share a tank, but watch one thing. A grown koi may treat small fancy goldfish as food, especially at night.

What temperature suits both koi and fancy goldfish?

65–74 °F. Koi need 59–77 °F, fancy goldfish need 65–74 °F.

What size tank do koi and fancy goldfish need together?

A pond. Koi outgrow indoor tanks.