Can congo tetras live with pencilfish?

Verdict
Yes

Yes. Congo tetras and pencilfish make a good pair. Both are fine at 75–82°F. Plan on at least 30 gal.

Congo tetraCongo tetra73–82°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: 75–82°Congo tetra 73–82°Pencilfish 75–82°
The green band is the temperature range both can live in.
456789Both: 6–7.5Congo tetra 6–7.5Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Congo tetra · 3 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

Congo tetraPencilfish
Temperature73–82 °F75–82 °F
pH6–7.55–7.5
Adult size3.0 in2.0 in
Minimum tank30 gal15 gal
TemperamentPeacefulPeaceful
Swims atMiddleMiddle
GroupGroups of 6+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for congo tetras

All congo tetra tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can congo tetras live with pencilfish?

Yes. Congo tetras and pencilfish make a good pair. Both are fine at 75–82°F. Plan on at least 30 gal.

What temperature suits both congo tetras and pencilfish?

75–82 °F. Congo tetras need 73–82 °F, pencilfish need 75–82 °F.

What size tank do congo tetras and pencilfish need together?

At least 30 gal, set by the congo tetra. Add space for each extra fish.