Can pencilfish live with dwarf neon rainbowfish?

Verdict
Yes

Yes. Pencilfish and dwarf neon rainbowfish get along in the same tank. Both are fine at 75–82°F. Plan on at least 20 gal.

PencilfishPencilfish75–82°F · pH 5–7.5 Dwarf neon rainbowfishDwarf neon rainbowfish75–82°F · pH 6.5–7.5

Why it works

Water side by side

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

Size to scale

Pencilfish · 2 inDwarf neon rainbowfish · 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

PencilfishDwarf neon rainbowfish
Temperature75–82 °F75–82 °F
pH5–7.56.5–7.5
Adult size2.0 in2.5 in
Minimum tank15 gal20 gal
TemperamentPeacefulPeaceful
Swims atMiddleMiddle
GroupGroups of 6+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for pencilfish

All pencilfish tank mates

Better tank mates for dwarf neon rainbowfish

All dwarf neon rainbowfish tank mates

Questions

Can pencilfish live with dwarf neon rainbowfish?

Yes. Pencilfish and dwarf neon rainbowfish get along in the same tank. Both are fine at 75–82°F. Plan on at least 20 gal.

What temperature suits both pencilfish and dwarf neon rainbowfish?

75–82 °F. Pencilfish need 75–82 °F, dwarf neon rainbowfish need 75–82 °F.

What size tank do pencilfish and dwarf neon rainbowfish need together?

At least 20 gal, set by the dwarf neon rainbowfish. Add space for each extra fish.