TankBud

Coral red pencilfish

Nannostomus mortenthaleri

Also known as Red Arc Pencilfish

FreshwaterFish

Coral red pencilfish (Nannostomus mortenthaleri)
Brian Gratwicke · CC BY 2.0

Care at a glance

Temperature
75–82°F
24–28°C
pH
5.5–7.0
Adult size
1.2 in
3 cm
Minimum tank
15 gal
55 L
Temperament
Peaceful
Social behavior
Shoaling
Swim level
Middle
Diet
Carnivore
Difficulty
Medium
Breeding
Medium
Rarity
Rare
Family
Lebiasinidae
Origin
Peru

Overview

The coral red pencilfish is a tiny, peaceful shoaling fish for the middle of a quiet planted tank. It suits a keeper with a little experience.

Did you know

Rival males put on a near-constant color show, sparring and flaring to sort out rank. They turn their brightest red during these standoffs. A single male kept alone never reaches that intensity, because there is nobody to compete with.

Caring for the coral red pencilfish

Keep coral red pencilfish in a small planted tank of at least 15 gal (55 L). A blackwater-style setup with dim light, tannins and lots of planting suits them and brings out their red. Keep the flow gentle, since these are small, delicate fish.

Aim for soft water that is acidic to neutral, at 75 to 82°F (24 to 28°C) and a pH of 5.5 to 7.0. Their mouths are small, so feed micro foods like crushed flake, micro pellets and tiny live or frozen items.

Keep them in a shoal of six or more. They hold the middle of the water and are peaceful, so pair them only with other gentle, small species. The males spar over rank without doing harm.

Males show the deepest red, while females are paler and rounder. Breeding them is possible but takes effort.

Good to know

The coral red pencilfish belongs to the family Lebiasinidae and was only described in 2001. In the wild it is a micropredator that eats very small invertebrates.

In the wild

Coral red pencilfish come from slow, clear streams in the Peruvian Amazon, around the Rio Nanay. The water is soft and acidic, full of leaf litter, roots and fine plants.

Weekly picks

Tank mates

The coral red 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 coral red pencilfish need?

A coral red pencilfish needs at least 15 gal (55 L). It spends most of its time in the middle.

What temperature and pH does a coral red pencilfish need?

A coral red pencilfish is comfortable at 75–82°F (24–28°C) with a pH of 5.5–7.0.

What does a coral red pencilfish eat?

A coral red pencilfish has a small mouth, so it eats micro foods. Feed it crushed flake, micro pellets and tiny live or frozen items.

How big does a coral red pencilfish get?

An adult coral red pencilfish reaches about 1.2 in (3 cm).

Does a coral red pencilfish need a group?

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

How can you tell a male coral red pencilfish from a female?

Males carry the deepest red, while females are paler and rounder.

Related species