Can serpae tetras live with pencilfish?

Verdict
Yes

Yes. Serpae tetras and pencilfish get along in the same tank. Both are fine at 75–79°F. Plan on at least 20 gal.

Serpae tetraSerpae tetra72–79°F · pH 6–7.5 PencilfishPencilfish75–82°F · pH 5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–79°Serpae tetra 72–79°Pencilfish 75–82°
The green band is the temperature range both can live in.
456789Both: 6–7.5Serpae tetra 6–7.5Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Serpae tetra · 1.75 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

Serpae tetraPencilfish
Temperature72–79 °F75–82 °F
pH6–7.55–7.5
Adult size1.75 in2.0 in
Minimum tank20 gal15 gal
TemperamentSemi-aggressivePeaceful
Swims atMiddleMiddle
GroupGroups of 6+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for serpae tetras

All serpae tetra tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can serpae tetras live with pencilfish?

Yes. Serpae tetras and pencilfish get along in the same tank. Both are fine at 75–79°F. Plan on at least 20 gal.

What temperature suits both serpae tetras and pencilfish?

75–79 °F. Serpae tetras need 72–79 °F, pencilfish need 75–82 °F.

What size tank do serpae tetras and pencilfish need together?

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