Can bettas live with pencilfish?

Verdict
Yes

Yes, bettas and pencilfish can live together. Both are fine at 76–82°F. Plan on at least 15 gal.

BettaBetta76–82°F · pH 6.5–7.5 PencilfishPencilfish75–82°F · pH 5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 76–82°Betta 76–82°Pencilfish 75–82°
The green band is the temperature range both can live in.
456789Both: 6.5–7.5Betta 6.5–7.5Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Betta · 2.5 inPencilfish · 2 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

BettaPencilfish
Temperature76–82 °F75–82 °F
pH6.5–7.55–7.5
Adult size2.5 in2.0 in
Minimum tank5 gal15 gal
TemperamentSemi-aggressivePeaceful
Swims atTopMiddle
GroupOne per tankGroups of 6+
DietCarnivoreOmnivore

Better tank mates for bettas

All betta tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can bettas live with pencilfish?

Yes, bettas and pencilfish can live together. Both are fine at 76–82°F. Plan on at least 15 gal.

What temperature suits both bettas and pencilfish?

76–82 °F. Bettas need 76–82 °F, pencilfish need 75–82 °F.

What size tank do bettas and pencilfish need together?

At least 15 gal, set by the pencilfish. Add space for each extra fish.