Can bettas live with killifish?

Verdict
Yes, with care

Yes, with care. Bettas and killifish can share a tank, but watch one thing. They only share 76–77°F. Keep the heater set there and steady.

BettaBetta76–82°F · pH 6.5–7.5 KillifishKillifish70–77°F · pH 5.5–7

What to watch

What works

Water side by side

55°60°65°70°75°80°85°90°Both: 76–77°Betta 76–82°Killifish 70–77°
The green band is the temperature range both can live in.
456789Both: 6.5–7Betta 6.5–7.5Killifish 5.5–7
The green band is the pH both tolerate.

Size to scale

Betta · 2.5 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

BettaKillifish
Temperature76–82 °F70–77 °F
pH6.5–7.55.5–7
Adult size2.5 in2.5 in
Minimum tank5 gal10 gal
TemperamentSemi-aggressivePeaceful
Swims atTopTop
GroupOne per tankAlone or in pairs
DietCarnivoreCarnivore

Better tank mates for bettas

All betta tank mates

Better tank mates for killifish

All killifish tank mates

Questions

Can bettas live with killifish?

Yes, with care. Bettas and killifish can share a tank, but watch one thing. They only share 76–77°F. Keep the heater set there and steady.

What temperature suits both bettas and killifish?

76–77 °F. Bettas need 76–82 °F, killifish need 70–77 °F.

What size tank do bettas and killifish need together?

At least 10 gal, set by the killifish. Add space for each extra fish.