Can rummy nose tetras live with pencilfish?

Verdict
Yes

Yes. Rummy nose tetras and pencilfish make a good pair. Both are fine at 75–82°F. Plan on at least 20 gal.

Rummy nose tetraRummy nose tetra75–84°F · pH 5.5–7 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°Rummy nose tetra 75–84°Pencilfish 75–82°
The green band is the temperature range both can live in.
456789Both: 5.5–7Rummy nose tetra 5.5–7Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Rummy nose tetra · 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

Rummy nose tetraPencilfish
Temperature75–84 °F75–82 °F
pH5.5–75–7.5
Adult size2.0 in2.0 in
Minimum tank20 gal15 gal
TemperamentPeacefulPeaceful
Swims atMiddleMiddle
GroupGroups of 6+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for rummy nose tetras

All rummy nose tetra tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can rummy nose tetras live with pencilfish?

Yes. Rummy nose tetras and pencilfish make a good pair. Both are fine at 75–82°F. Plan on at least 20 gal.

What temperature suits both rummy nose tetras and pencilfish?

75–82 °F. Rummy nose tetras need 75–84 °F, pencilfish need 75–82 °F.

What size tank do rummy nose tetras and pencilfish need together?

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