Can rainbow sharks live with killifish?

Verdict
Yes

Yes. Rainbow sharks and killifish make a good pair. Both are fine at 72–77°F. Plan on at least 55 gal.

Rainbow sharkRainbow shark72–80°F · pH 6.5–7.5 KillifishKillifish70–77°F · pH 5.5–7

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 72–77°Rainbow shark 72–80°Killifish 70–77°
The green band is the temperature range both can live in.
456789Both: 6.5–7Rainbow shark 6.5–7.5Killifish 5.5–7
The green band is the pH both tolerate.

Size to scale

Rainbow shark · 6 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

Rainbow sharkKillifish
Temperature72–80 °F70–77 °F
pH6.5–7.55.5–7
Adult size6.0 in2.5 in
Minimum tank55 gal10 gal
TemperamentSemi-aggressivePeaceful
Swims atBottomTop
GroupOne per tankAlone or in pairs
DietOmnivoreCarnivore

Better tank mates for rainbow sharks

All rainbow shark tank mates

Better tank mates for killifish

All killifish tank mates

Questions

Can rainbow sharks live with killifish?

Yes. Rainbow sharks and killifish make a good pair. Both are fine at 72–77°F. Plan on at least 55 gal.

What temperature suits both rainbow sharks and killifish?

72–77 °F. Rainbow sharks need 72–80 °F, killifish need 70–77 °F.

What size tank do rainbow sharks and killifish need together?

At least 55 gal, set by the rainbow shark. Add space for each extra fish.