Pencilfish (Golden, Red, Dwarf) – Types, Care, Size, Feeding & Details!

Pencilfish (Nannostomus) have various types like Dwarf Pencilfish, Red Pencilfish, Golden Pencilfish, etc. It is a genus of freshwater ray-finned fish from the Lebiasinidae family.

It currently includes about 20 species. The name of the genus in Greek means “small mouth”, which is indicated not by the small size of representatives whose body length rarely exceeds 3 cm.

Quick Stats

Scientific Name: Nannostomus
Family: Lebiasinidae
Lifespan: 5 Years
Nature: Peace-Loving Fish
Temperature: 64° – 82° F (18° – 27.7° C)
pH: 5.0 – 8.0
Minimum tank size: 10 Gallons
Origin: South America

General Description

Lovers of small aquariums often face the problem of selecting the right fishes for their small volume aquariums and Pencilfish is certainly one of the most looked after candidates for this.

This is due to the fact that the size of the majority of representatives of this fish barely reaches 3 cm, therefore, even keeping them in a pack, An aquarium of 30-40 liters will suffice for many species.

They lead a gregarious lifestyle. In general, These are peaceful fish, which, nevertheless, zealously guard their territory. A strict hierarchy is established in the flocks. The individual with the highest status in the group often takes an upright position.

Pencilfish prefers to stay at the top of the tank. Their main activity is observed in the evening as during the day pencilfish prefer to swim freely in the water.

One of the interesting features of Pencilfish is the color change during the day. At dusk, the color of the fish becomes lighter. Unfortunately, the exact cause of this phenomenon has not yet been established.

In our article, we will talk about the most popular types of nannostomus and the conditions required for these small fish.


Pencilfish has an elongated and slightly compressed lateral body. The muzzle is pointed and the mouth opening is small. The fins are short and small. The tail is two-bladed. The adipose fin is not available for all species.

The maximum body size of a Pencilfish is about 6 cm, but usually smaller.

Body coloration is varied. There are nondescript individuals with a silver torso and rather bright representatives with red stripes.

Longitudinal stripes along the body are also characteristic of many species. The fins are colorless or reddish. At night, the color can change beyond recognition.

The life expectancy of Pencilfish in comfortable conditions is about 5 years.


The homeland of the Pencilfish is South America. This fish can be found in the Amazon and Rio Negro.

They gravitate towards heavily overgrown water bodies with a large number of snags. From the numerous litter of leaves of tropical trees, water is saturated with humic substances, which give it a characteristic “black” shade.

Pencilfish Types

Golden Pencilfish (Nannostomus Beckfordi)

The most famous and common among aquarists is the Golden Pencilfish. The species lives in a vast area in the lower reaches of the Amazon River.

Golden Pencilfish rarely grows more than 4 cm long. The main body color is reddish-brown or pinkish.

In the middle of the body from the mouth to the tail stretches a wide dark strip passing through the eye. The pectoral fins are transparent, the rest have bright red spots at the base. The adipose fin is absent.

At night, the color of the fish fades, and three black spots appear on the body. Distinguishing a male from a female is usually not difficult: males are smaller in size, but brighter in color.

Females, in turn, are the owners of a rounded abdomen and gold edging at a dark stripe.

It is recommended to keep Golden Pencilfish in flocks of 10 or more. Therefore, the aquarium should have a volume of 50-60 liters.

It is better to use natural stones and driftwood in the design, as well as create islands of dense greenery.

Golden Pencilfish gets along well with small species that are not prone to aggression.

Dwarf Pencilfish (Nannostomus Marginatus)

The usual size of dwarf pencilfish is 2.5 – 3 cm, for which the species got its name. It is widespread in almost the entire Amazon basin from source to mouth.

The body color is silver, there is a characteristic wide black stripe from head to tail, just above it is another, narrower one. The pelvic and caudal fins are transparent; the rest have a red spot at the base.

At night, the color is paler and the stripes disappear.

Dwarf pencilfish are social fish. The number of individuals in a flock is a minimum of 10 fish. The small size allows dwarf pencilfish to be kept in small aquariums from 30 liters.

The dwarf pencilfish prefers the upper and middle layers of the aquarium.

They get along well with their relatives, as well as with other proportionate and peace-loving fish.

Red Pencilfish (Nannostomus Mortenthaleri)

One of the most beautiful representatives of this family. Most of the body is painted in bright red color, with which the black stripes contrast excellently.

The abdomen is light, sometimes almost white. The size of adults is about 3 cm.

Red Pencilfish are found in the rivers of Peru. These fish are sensitive to the parameters of the water in the aquarium, deviations from the optimal values ​​are very likely to lead to diseases.

It is better to keep Red Pencilfish in flocks of 6 or more, the minimum recommended aquarium should have a volume of 30 liters.

Despite the success in artificial reproduction, wild-caught individuals still dominate the market.

Pencilfish Care and maintenance

The small size of pencilfish allows them to be kept in fairly small aquariums. For example, a flock of 8-10 individuals will have an aquarium of 60 liters. It is necessary to keep pencilfish strictly in groups.

Pencilfish will get stressed if you keep them single or pair.

It is recommended to decorate your aquarium in a natural style using natural snags and stones. There must be areas with dense thickets of aquatic plants and floating species to create semi-darkness.

It is advised to use a dark and small fraction of soil, suitable for growing live plants. Quartz sand is also a good choice.

The aquarium will need a standard set of equipment – a filter, a compressor, and a thermostat. Once a week, it is necessary to replace up to 20% of the volume of the aquarium with the obligatory cleaning of the soil.

It is useful to enrich the water with natural humic substances similar to natural ones.

The optimal water parameters for the content are: T = 24-28 ° C, pH = 6.0-8.0, GH = 5-19.

Pencilfish Tank Mates

Pencilfish are small and peace-loving fishes and they prefer living with other peace-loving tank mates in the aquarium.

You can easily keep your pencilfish with small and calm fishes like Neon Tetras, Black Neon Tetra, Glowlight Tetra, Minnow Fish, Guppy Fish, Cory Catfish, Oto Catfish, Zebrafish, Harlequin Rasboras

Large and medium cichlids and goldfish are not suitable tank mates for pencilfish.

In aquariums of bigger size, it is allowed to combine several different types of nannostomus together, The main thing required is that there should be many shelters in the tank.

Feeding Pencilfish

When choosing the optimal food for pencilfish, it is necessary to take into account the small size of their mouth opening. It is better not to feed them with live and frozen food, which cannot fully satisfy the nutritional needs of the fish, and in the worst case can cause disease.

A more suitable and convenient option is to feed the pencilfish with high-quality dry food, which is balanced in basic nutrients, contains vitamins and functional additives that affect color, digestive system, and immunity.

Tetra Micro Crisps is a high-quality nutrient chip food specially formulated for small ornamental fishes. A balanced formula combines ingredients of plant and animal origin.

The food is highly digestible, which helps to keep the water in the aquarium clean.

A good alternative is the “classic” TetraMin flake food. It is made from over 40 high-quality ingredients and therefore has a high nutritional value.

The prebiotics in the composition supports the proper functioning of digestion.

The flakes are easily crushed by hand and float for a long time on the surface of the water, which allows nannostomuses to get enough of them.

Breeding Pencilfish

To breed pencilfish at home, you will need a spawning aquarium with a volume of 5-10 liters, on the bottom of which a separator mesh or more small-leaved plants, such as Javan moss, are laid.

Provide low aeration and dim lighting.

Sexual maturity in fish occurs at the age of 8-10 months.

Spawning is possible both in pairs and in groups. In any case, a week before the process, males and females must be separated and heavily fed.

Parents are kept in a spawning aquarium and to stimulate spawning, You need to raise the temperature and soften the water.

These fish spawn usually at night time. The female lays several hundred eggs on the leaves of plants; in some species, the female prefers the roots of floating plants.

After the producers have laid eggs, they are removed from the spawning aquarium, and it is darkened.

After 1-2 days, larvae hatch, which is less than a week begins to feed on their own.

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