Can killifish live with firemouth cichlids?

Verdict
Yes

Yes, killifish and firemouth cichlids can live together. Both are fine at 75–77°F. Plan on at least 30 gal.

KillifishKillifish70–77°F · pH 5.5–7 Firemouth cichlidFiremouth cichlid75–86°F · pH 6.5–8

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–77°Killifish 70–77°Firemouth cichlid 75–86°
The green band is the temperature range both can live in.
456789Both: 6.5–7Killifish 5.5–7Firemouth cichlid 6.5–8
The green band is the pH both tolerate.

Size to scale

Killifish · 2.5 inFiremouth cichlid · 6 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

KillifishFiremouth cichlid
Temperature70–77 °F75–86 °F
pH5.5–76.5–8
Adult size2.5 in6.0 in
Minimum tank10 gal30 gal
TemperamentPeacefulSemi-aggressive
Swims atTopBottom
GroupAlone or in pairsAlone or in pairs
DietCarnivoreOmnivore

Better tank mates for killifish

All killifish tank mates

Better tank mates for firemouth cichlids

All firemouth cichlid tank mates

Questions

Can killifish live with firemouth cichlids?

Yes, killifish and firemouth cichlids can live together. Both are fine at 75–77°F. Plan on at least 30 gal.

What temperature suits both killifish and firemouth cichlids?

75–77 °F. Killifish need 70–77 °F, firemouth cichlids need 75–86 °F.

What size tank do killifish and firemouth cichlids need together?

At least 30 gal, set by the firemouth cichlid. Add space for each extra fish.