Can koi live with plecos?

Verdict
Yes

Yes. Koi and plecos get along in the same tank. Both are fine at 72–77°F. Plan on at least Pond.

KoiKoi59–77°F · pH 7–8.5 Common plecoCommon pleco72–86°F · pH 6.5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 72–77°Koi 59–77°Common pleco 72–86°
The green band is the temperature range both can live in.
456789Both: 7–7.5Koi 7–8.5Common pleco 6.5–7.5
The green band is the pH both tolerate.

Size to scale

Koi · 24 inCommon pleco · 15 in0"6"12"18"24"
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

KoiCommon pleco
Temperature59–77 °F72–86 °F
pH7–8.56.5–7.5
Adult size24.0 in15.0 in
Minimum tankPond125 gal
TemperamentPeacefulPeaceful
Swims atAll levelsBottom
GroupGroups of 3+Alone or in pairs
DietOmnivoreHerbivore

Better tank mates for koi

All koi tank mates

Better tank mates for plecos

All common pleco tank mates

Questions

Can koi live with plecos?

Yes. Koi and plecos get along in the same tank. Both are fine at 72–77°F. Plan on at least Pond.

What temperature suits both koi and plecos?

72–77 °F. Koi need 59–77 °F, plecos need 72–86 °F.

What size tank do koi and plecos need together?

A pond. Koi outgrow indoor tanks.