Can koi live with harlequin rasboras?

Verdict

Yes, with care

Yes, with care. Koi and harlequin rasboras can share a tank, but watch one thing. At 24 inches a koi can swallow a small harlequin rasbora. Fast, alert fish usually stay out of reach.

Koi59–77°F · pH 7–8.5

Harlequin rasbora72–80°F · pH 6–7.5

What to watch

Watch outAt 24 inches a koi can swallow a small harlequin rasbora. Fast, alert fish usually stay out of reach.

What works

Both are fine at 72–77°F.
pH 7–7.5 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	Harlequin rasbora
Temperature	59–77 °F	72–80 °F
pH	7–8.5	6–7.5
Adult size	24.0 in	2.0 in
Minimum tank	Pond	10 gal
Temperament	Peaceful	Peaceful
Swims at	All levels	Middle
Group	Groups of 3+	Groups of 6+
Diet	Omnivore	Omnivore

Better tank mates for koi

All koi tank mates

Better tank mates for harlequin rasboras

All harlequin rasbora tank mates

Questions

Can koi live with harlequin rasboras?

Yes, with care. Koi and harlequin rasboras can share a tank, but watch one thing. At 24 inches a koi can swallow a small harlequin rasbora. Fast, alert fish usually stay out of reach.

What temperature suits both koi and harlequin rasboras?

72–77 °F. Koi need 59–77 °F, harlequin rasboras need 72–80 °F.

What size tank do koi and harlequin rasboras need together?

A pond. Koi outgrow indoor tanks.