Dwarf pencilfish

Nannostomus marginatus

FreshwaterFish

Care at a glance

Temperature
72–82°F
22–28°C
pH
5.0–7.0
Adult size
1 in
2.5 cm
Minimum tank
12 gal
45 L
Temperament
Peaceful
Social behavior
Shoaling
Swim level
Middle
Difficulty
Medium
Breeding
Medium
Rarity
Rare
Family
Lebiasinidae
Origin
Peru, Colombia, Brazil

Overview

Keep dwarf pencilfish in a group of at least six, in a tank of around 45 liters or more. They hold the middle of the water and move in a slow, deliberate way rather than darting. Their mouths are tiny, so feed small foods like crushed flakes, micro-pellets, baby brine shrimp, and daphnia. They are peaceful and best matched with other small, calm fish in soft, acidic water.

In the wild

Dwarf pencilfish live in slow, heavily planted blackwater across Peru, Colombia, and Brazil, in streams and flooded forest with leaf litter underfoot. The water is soft, acidic, and dark with tannins. A tank with dim lighting, fine plants, driftwood, and dried leaves suits them, with a pH on the low side, down toward 5 to 7. Keep flow gentle and the water warm.

Good to know

This is a pencilfish in the family Lebiasinidae, one of the smaller species at around 2.5 cm. The slim body carries a dark horizontal stripe with bordering lines and red on the fins. It is an egg scatterer, and breeding takes some effort. It does best in warm, soft, acidic water in the mid to high 20s C.

Did you know

Like other pencilfish, they switch their coloring at night. The crisp daytime stripe breaks up into a blotchy pattern once the lights go out, then snaps back in the morning.

Weekly picks

Tank mates

Dwarf pencilfish is a peaceful, shoaling species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.

Check the full mix in the stocking calculator

Common questions

What size tank does a Dwarf pencilfish need?

A Dwarf pencilfish needs at least 12 gal (45 L). It spends most of its time in the middle.

What temperature and pH does a Dwarf pencilfish need?

A Dwarf pencilfish is comfortable at 72–82°F (22–28°C) with a pH of 5.0–7.0.

How big does a Dwarf pencilfish get?

An adult Dwarf pencilfish reaches about 1 in (2.5 cm).

Does a Dwarf pencilfish need a group?

Yes. A Dwarf pencilfish is a shoaling species and should be kept in a group, not singly.

Related species