Can killifish live with hatchetfish?

Verdict
Yes

Yes. Killifish and hatchetfish get along in the same tank. Both are fine at 75–77°F. Plan on at least 20 gal.

KillifishKillifish70–77°F · pH 5.5–7 HatchetfishHatchetfish75–81°F · pH 5.5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–77°Killifish 70–77°Hatchetfish 75–81°
The green band is the temperature range both can live in.
456789Both: 5.5–7Killifish 5.5–7Hatchetfish 5.5–7.5
The green band is the pH both tolerate.

Size to scale

Killifish · 2.5 inHatchetfish · 1.5 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

KillifishHatchetfish
Temperature70–77 °F75–81 °F
pH5.5–75.5–7.5
Adult size2.5 in1.5 in
Minimum tank10 gal20 gal
TemperamentPeacefulPeaceful
Swims atTopTop
GroupAlone or in pairsGroups of 6+
DietCarnivoreCarnivore

Better tank mates for killifish

All killifish tank mates

Better tank mates for hatchetfish

All hatchetfish tank mates

Questions

Can killifish live with hatchetfish?

Yes. Killifish and hatchetfish get along in the same tank. Both are fine at 75–77°F. Plan on at least 20 gal.

What temperature suits both killifish and hatchetfish?

75–77 °F. Killifish need 70–77 °F, hatchetfish need 75–81 °F.

What size tank do killifish and hatchetfish need together?

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