Can killifish live with black neon tetras?

Verdict
Yes

Yes. Killifish and black neon tetras make a good pair. Both are fine at 73–77°F. Plan on at least 15 gal.

KillifishKillifish70–77°F · pH 5.5–7 Black neon tetraBlack neon tetra73–81°F · pH 5.5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 73–77°Killifish 70–77°Black neon tetra 73–81°
The green band is the temperature range both can live in.
456789Both: 5.5–7Killifish 5.5–7Black neon tetra 5.5–7.5
The green band is the pH both tolerate.

Size to scale

Killifish · 2.5 inBlack neon tetra · 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

KillifishBlack neon tetra
Temperature70–77 °F73–81 °F
pH5.5–75.5–7.5
Adult size2.5 in1.5 in
Minimum tank10 gal15 gal
TemperamentPeacefulPeaceful
Swims atTopMiddle
GroupAlone or in pairsGroups of 6+
DietCarnivoreOmnivore

Better tank mates for killifish

All killifish tank mates

Better tank mates for black neon tetras

All black neon tetra tank mates

Questions

Can killifish live with black neon tetras?

Yes. Killifish and black neon tetras make a good pair. Both are fine at 73–77°F. Plan on at least 15 gal.

What temperature suits both killifish and black neon tetras?

73–77 °F. Killifish need 70–77 °F, black neon tetras need 73–81 °F.

What size tank do killifish and black neon tetras need together?

At least 15 gal, set by the black neon tetra. Add space for each extra fish.