Can guppies live with pencilfish?

Verdict
Yes

Yes. Guppies and pencilfish get along in the same tank. Both are fine at 75–82°F. Plan on at least 15 gal.

GuppyGuppy72–82°F · pH 6.8–7.8 PencilfishPencilfish75–82°F · pH 5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–82°Guppy 72–82°Pencilfish 75–82°
The green band is the temperature range both can live in.
456789Both: 6.8–7.5Guppy 6.8–7.8Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Guppy · 2 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

GuppyPencilfish
Temperature72–82 °F75–82 °F
pH6.8–7.85–7.5
Adult size2.0 in2.0 in
Minimum tank10 gal15 gal
TemperamentPeacefulPeaceful
Swims atTopMiddle
GroupGroups of 3+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for guppies

All guppy tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can guppies live with pencilfish?

Yes. Guppies and pencilfish get along in the same tank. Both are fine at 75–82°F. Plan on at least 15 gal.

What temperature suits both guppies and pencilfish?

75–82 °F. Guppies need 72–82 °F, pencilfish need 75–82 °F.

What size tank do guppies and pencilfish need together?

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