Can pencilfish live with endlers?

Verdict
Yes

Yes, pencilfish and endlers can live together. Both are fine at 75–82°F. Plan on at least 15 gal.

PencilfishPencilfish75–82°F · pH 5–7.5 Endler's livebearerEndler's livebearer72–82°F · pH 7–8

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–82°Pencilfish 75–82°Endler's livebearer 72–82°
The green band is the temperature range both can live in.
456789Both: 7–7.5Pencilfish 5–7.5Endler's livebearer 7–8
The green band is the pH both tolerate.

Size to scale

Pencilfish · 2 inEndler's livebearer · 1 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

PencilfishEndler's livebearer
Temperature75–82 °F72–82 °F
pH5–7.57–8
Adult size2.0 in1.0 in
Minimum tank15 gal5 gal
TemperamentPeacefulPeaceful
Swims atMiddleTop
GroupGroups of 6+Groups of 3+
DietOmnivoreOmnivore

Better tank mates for pencilfish

All pencilfish tank mates

Better tank mates for endlers

All endler's livebearer tank mates

Questions

Can pencilfish live with endlers?

Yes, pencilfish and endlers can live together. Both are fine at 75–82°F. Plan on at least 15 gal.

What temperature suits both pencilfish and endlers?

75–82 °F. Pencilfish need 75–82 °F, endlers need 72–82 °F.

What size tank do pencilfish and endlers need together?

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