Can mollies live with pencilfish?

Verdict

Yes, with care

Yes, with care. Mollies and pencilfish can share a tank, but watch one thing. Water chemistry is a squeeze. The only pH that suits both is around 7.5.

Molly72–82°F · pH 7.5–8.5

Pencilfish75–82°F · pH 5–7.5

What to watch

Watch outWater chemistry is a squeeze. The only pH that suits both is around 7.5.

What works

Both are fine at 75–82°F.
They use different parts of the tank: mollies the top, pencilfish the mid.

Water side by side

The green band is the temperature range both can live in.

The green band is the pH both tolerate.

Size to scale

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

	Molly	Pencilfish
Temperature	72–82 °F	75–82 °F
pH	7.5–8.5	5–7.5
Adult size	4.0 in	2.0 in
Minimum tank	20 gal	15 gal
Temperament	Peaceful	Peaceful
Swims at	Top	Middle
Group	Groups of 3+	Groups of 6+
Diet	Omnivore	Omnivore

Better tank mates for mollies

All molly tank mates

Better tank mates for pencilfish

All pencilfish tank mates

Questions

Can mollies live with pencilfish?

Yes, with care. Mollies and pencilfish can share a tank, but watch one thing. Water chemistry is a squeeze. The only pH that suits both is around 7.5.

What temperature suits both mollies and pencilfish?

75–82 °F. Mollies need 72–82 °F, pencilfish need 75–82 °F.

What size tank do mollies and pencilfish need together?

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