Can otocinclus live with killifish?

Verdict
Yes

Yes. Otocinclus and killifish make a good pair. Both are fine at 72–77°F. Plan on at least 20 gal.

OtocinclusOtocinclus72–79°F · pH 6–7.5 KillifishKillifish70–77°F · pH 5.5–7

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 72–77°Otocinclus 72–79°Killifish 70–77°
The green band is the temperature range both can live in.
456789Both: 6–7Otocinclus 6–7.5Killifish 5.5–7
The green band is the pH both tolerate.

Size to scale

Otocinclus · 2 inKillifish · 2.5 in0"1"2"3"4"5"6"
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

OtocinclusKillifish
Temperature72–79 °F70–77 °F
pH6–7.55.5–7
Adult size2.0 in2.5 in
Minimum tank20 gal10 gal
TemperamentPeacefulPeaceful
Swims atBottomTop
GroupGroups of 6+Alone or in pairs
DietHerbivoreCarnivore

Better tank mates for otocinclus

All otocinclus tank mates

Better tank mates for killifish

All killifish tank mates

Questions

Can otocinclus live with killifish?

Yes. Otocinclus and killifish make a good pair. Both are fine at 72–77°F. Plan on at least 20 gal.

What temperature suits both otocinclus and killifish?

72–77 °F. Otocinclus need 72–79 °F, killifish need 70–77 °F.

What size tank do otocinclus and killifish need together?

At least 20 gal, set by the otocinclus. Add space for each extra fish.