Can crayfish live with killifish?

Verdict
Yes

Yes. Crayfish and killifish make a good pair. Both are fine at 70–77°F. Plan on at least 20 gal.

CrayfishCrayfish65–77°F · pH 6.5–8 KillifishKillifish70–77°F · pH 5.5–7

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 70–77°Crayfish 65–77°Killifish 70–77°
The green band is the temperature range both can live in.
456789Both: 6.5–7Crayfish 6.5–8Killifish 5.5–7
The green band is the pH both tolerate.

Size to scale

Crayfish · 5 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

CrayfishKillifish
Temperature65–77 °F70–77 °F
pH6.5–85.5–7
Adult size5.0 in2.5 in
Minimum tank20 gal10 gal
TemperamentAggressivePeaceful
Swims atBottomTop
GroupOne per tankAlone or in pairs
DietOmnivoreCarnivore

Better tank mates for crayfish

All crayfish tank mates

Better tank mates for killifish

All killifish tank mates

Questions

Can crayfish live with killifish?

Yes. Crayfish and killifish make a good pair. Both are fine at 70–77°F. Plan on at least 20 gal.

What temperature suits both crayfish and killifish?

70–77 °F. Crayfish need 65–77 °F, killifish need 70–77 °F.

What size tank do crayfish and killifish need together?

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