Can crayfish live with pencilfish?

Verdict
Yes

Yes. Crayfish and pencilfish make a good pair. Both are fine at 75–77°F. Plan on at least 20 gal.

CrayfishCrayfish65–77°F · pH 6.5–8 PencilfishPencilfish75–82°F · pH 5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–77°Crayfish 65–77°Pencilfish 75–82°
The green band is the temperature range both can live in.
456789Both: 6.5–7.5Crayfish 6.5–8Pencilfish 5–7.5
The green band is the pH both tolerate.

Size to scale

Crayfish · 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

CrayfishPencilfish
Temperature65–77 °F75–82 °F
pH6.5–85–7.5
Adult size5.0 in2.0 in
Minimum tank20 gal15 gal
TemperamentAggressivePeaceful
Swims atBottomMiddle
GroupOne per tankGroups of 6+
DietOmnivoreOmnivore

Better tank mates for crayfish

All crayfish tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can crayfish live with pencilfish?

Yes. Crayfish and pencilfish make a good pair. Both are fine at 75–77°F. Plan on at least 20 gal.

What temperature suits both crayfish and pencilfish?

75–77 °F. Crayfish need 65–77 °F, pencilfish need 75–82 °F.

What size tank do crayfish and pencilfish need together?

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