Can hatchetfish live with pencilfish?

Verdict
Yes

Yes. Hatchetfish and pencilfish get along in the same tank. Both are fine at 75–81°F. Plan on at least 20 gal.

HatchetfishHatchetfish75–81°F · pH 5.5–7.5 PencilfishPencilfish75–82°F · pH 5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–81°Hatchetfish 75–81°Pencilfish 75–82°
The green band is the temperature range both can live in.
456789Both: 5.5–7.5Hatchetfish 5.5–7.5Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Hatchetfish · 1.5 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

HatchetfishPencilfish
Temperature75–81 °F75–82 °F
pH5.5–7.55–7.5
Adult size1.5 in2.0 in
Minimum tank20 gal15 gal
TemperamentPeacefulPeaceful
Swims atTopMiddle
GroupGroups of 6+Groups of 6+
DietCarnivoreOmnivore

Better tank mates for hatchetfish

All hatchetfish tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can hatchetfish live with pencilfish?

Yes. Hatchetfish and pencilfish get along in the same tank. Both are fine at 75–81°F. Plan on at least 20 gal.

What temperature suits both hatchetfish and pencilfish?

75–81 °F. Hatchetfish need 75–81 °F, pencilfish need 75–82 °F.

What size tank do hatchetfish and pencilfish need together?

At least 20 gal, set by the hatchetfish. Add space for each extra fish.