Can goldfish live with pencilfish?

Verdict
No

No. Goldfish and pencilfish should not share a tank. Goldfish are coldwater animals (60–74°F); pencilfish need 75–82°F. No temperature suits both.

GoldfishGoldfish60–74°F · pH 7–8 PencilfishPencilfish75–82°F · pH 5–7.5

What to watch

What works

Water side by side

55°60°65°70°75°80°85°90°Goldfish 60–74°Pencilfish 75–82°
The ranges do not meet, so one of them would always be too warm or too cold.
456789Both: 7–7.5Goldfish 7–8Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Goldfish · 10 inPencilfish · 2 in0"2"4"6"8"10"
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

GoldfishPencilfish
Temperature60–74 °F75–82 °F
pH7–85–7.5
Adult size10.0 in2.0 in
Minimum tank40 gal15 gal
TemperamentPeacefulPeaceful
Swims atAll levelsMiddle
GroupAlone or in pairsGroups of 6+
DietOmnivoreOmnivore

Better tank mates for goldfish

All goldfish tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can goldfish live with pencilfish?

No. Goldfish and pencilfish should not share a tank. Goldfish are coldwater animals (60–74°F); pencilfish need 75–82°F. No temperature suits both.

What temperature suits both goldfish and pencilfish?

None. Goldfish need 60–74 °F and pencilfish need 75–82 °F, so the ranges do not meet.

What size tank do goldfish and pencilfish need together?

At least 40 gal, set by the goldfish. Add space for each extra fish.