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Marilyn's pencilfish

Nannostomus marilynae

Also known as Greenstripe pencilfish, Green striped pencilfish

FreshwaterFish

Marilyn's pencilfish (Nannostomus marilynae)
The Wet Spot Tropical Fish · Used with permission

Care at a glance

Temperature
73–81°F
23–27°C
pH
5.0–6.8
Adult size
2 in
5 cm
Minimum tank
14 gal
54 L
Temperament
Peaceful
Social behavior
Schooling
Swim level
Middle
Difficulty
Medium
Breeding
No record
Rarity
Rare
Family
Lebiasinidae
Origin
Upper Negro and Orinoco tributaries

Overview

Marilyn's pencilfish is an elegant, peaceful pencilfish that schools in the midwater. It holds its body at a slight upward tilt, as pencilfish do. It is best with a little experience, a step up from the easiest fish.

Did you know

Marilyn's pencilfish is named for Marilyn Weitzman, an American ichthyologist who worked on South American fishes with her husband, Stanley. It was described and named for her in 1975.

Caring for the Marilyn's pencilfish

Keep Marilyn's pencilfish in a group of six or more, in a tank of at least 14 gal (54 L). A group schools naturally and shows off the greenish side stripe, while single fish hide and fade. A mature, thickly planted tank with dark substrate, driftwood and leaf litter suits them, with soft light and open midwater to swim in.

Give them soft, acidic water at 73 to 81°F (23 to 27°C) and a pH of 5.0 to 6.8. In the wild they feed on small invertebrates. Feed small foods they can manage, such as crushed flake, micro pellets, cyclops, daphnia and baby brine shrimp.

Marilyn's pencilfish are peaceful and easygoing. They fit a soft-water community of small tetras, dwarf cichlids and other gentle fish. As with many pencilfishes, spawning in the aquarium is not well documented for this species.

Good to know

Marilyn's pencilfish belongs to the pencilfish family Lebiasinidae. It is a slim bronze fish, set apart from its many red-striped relatives by a green-toned lateral stripe. That stripe gives it its other common name, the greenstripe pencilfish.

In the wild

Marilyn's pencilfish lives in soft, acidic, tea-stained waters of the upper Rio Negro and Orinoco tributaries, in Brazil, Venezuela and Colombia. It keeps to sluggish backwaters and dense marginal plants.

Weekly picks

Tank mates

The Marilyn's pencilfish is a peaceful, schooling 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 Marilyn's pencilfish need?

A Marilyn's pencilfish needs at least 14 gal (54 L). It spends most of its time in the middle.

What temperature and pH does a Marilyn's pencilfish need?

A Marilyn's pencilfish is comfortable at 73–81°F (23–27°C) with a pH of 5.0–6.8.

What does a Marilyn's pencilfish eat?

A Marilyn's pencilfish feeds on small invertebrates in the wild. In the tank, it eats small foods it can manage, such as crushed flake, micro pellets, cyclops, daphnia and baby brine shrimp.

How big does a Marilyn's pencilfish get?

An adult Marilyn's pencilfish reaches about 2 in (5 cm).

Does a Marilyn's pencilfish need a group?

Yes. A Marilyn's pencilfish is a schooling species and should be kept in a group, not singly.

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