Can black skirt tetras live with pencilfish?

Verdict
Yes

Yes. Black skirt tetras and pencilfish get along in the same tank. Both are fine at 75–80°F. Plan on at least 15 gal.

Black skirt tetraBlack skirt tetra70–80°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: 75–80°Black skirt tetra 70–80°Pencilfish 75–82°
The green band is the temperature range both can live in.
456789Both: 6–7.5Black skirt tetra 6–7.5Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Black skirt tetra · 2.5 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

Black skirt tetraPencilfish
Temperature70–80 °F75–82 °F
pH6–7.55–7.5
Adult size2.5 in2.0 in
Minimum tank15 gal15 gal
TemperamentSemi-aggressivePeaceful
Swims atMiddleMiddle
GroupGroups of 6+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for black skirt tetras

All black skirt tetra tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can black skirt tetras live with pencilfish?

Yes. Black skirt tetras and pencilfish get along in the same tank. Both are fine at 75–80°F. Plan on at least 15 gal.

What temperature suits both black skirt tetras and pencilfish?

75–80 °F. Black skirt tetras need 70–80 °F, pencilfish need 75–82 °F.

What size tank do black skirt tetras and pencilfish need together?

At least 15 gal, set by the black skirt tetra. Add space for each extra fish.