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Three-lined pencilfish

Nannostomus trifasciatus

Also known as Three Line Pencilfish

FreshwaterFish

Three-lined pencilfish (Nannostomus trifasciatus)
Tsunamicarlos · Public domain

Care at a glance

Temperature
72–82°F
22–28°C
pH
5.5–7.0
Adult size
1.3 in
3.3 cm
Minimum tank
15 gal
55 L
Temperament
Peaceful
Social behavior
Shoaling
Swim level
Middle
Difficulty
Medium
Breeding
Medium
Rarity
Rare
Family
Lebiasinidae
Origin
South America

Overview

Keep it in a group of at least six, ideally more, in a tank around 55 liters with plenty of plant cover. It holds in the middle and upper water and can be shy, so it shows best in a calm setup. Water should be soft and acidic, pH 5.5 to 7, at 22 to 28 C. Its mouth is tiny, so feed small foods: micro-pellets, fine flake, and little live or frozen items like daphnia, baby brine shrimp, and microworms. It is gentle and suits a quiet, similar-sized community.

In the wild

The three-lined pencilfish lives in slow blackwater streams and tributaries of the Amazon basin, in Brazil, Peru, and Colombia. The water there is acidic, soft, and stained brown with tannins, with leaf litter and plants everywhere. To match it, run a dim, planted tank with driftwood, dried leaves, and maybe some peat or botanicals to soften and tint the water. Keep it in the low to high 20s C.

Good to know

This is a pencilfish in the family Lebiasinidae, a slim, small species reaching only about 3.3 cm. It has three dark horizontal stripes down a slender body. Like other pencilfish, its day pattern shifts at night into a blotchy resting pattern. It is an egg-scattering species that is moderately tricky to breed.

Did you know

Pencilfish change their look between day and night. The clear daytime stripes break up into a spotted or banded pattern after lights-out, which can be a surprise the first time you check the tank in the dark. It's a normal resting color, not stress.

Weekly picks

Tank mates

Three-lined 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 Three-lined pencilfish need?

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

What temperature and pH does a Three-lined pencilfish need?

A Three-lined pencilfish is comfortable at 72–82°F (22–28°C) with a pH of 5.5–7.0.

How big does a Three-lined pencilfish get?

An adult Three-lined pencilfish reaches about 1.3 in (3.3 cm).

Does a Three-lined pencilfish need a group?

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

Related species