Information, Characiformes (Characins), Freshwater fish, Pencilfish, Species

Pencilfish: Complete Species & Care Overview

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by Jason Matthews



Pencilfish is a tiny freshwater fish species popular in the aquarium industry. This variety belongs to the pipefish family and is known for its unique body features. They also exhibit unique behaviors that are different from schooling fish. Therefore, they are a perfect fit if you are looking for nano fish for your community tank.

This guide will provide all the information you need to know about the pencilfish, from appearance, tank size, conditions, and breeding requirements to dietary needs.


Scientific Name: Lebiasinidae
Common Names: Pencilfish, Peruvian red pencilfish, ruby red pencilfish, and red arc pencilfish
Life Expectancy: 4 to 5 years
Adult Size: 1.5 to 2 inches


Primary DietOmnivores
Beginner FriendlyIntermediate
Tank PreferenceTop dweller
Water Temperature72-78F
Tank Size20-30 gallon
Water ParametersA pH of 6.5-7.5, water hardness of 9-20 dGH

Fun Fact Corner

Pencilfish get their name from their appearance. Their long bodies have black stripes that make them look like a pencil.


Pencilfish are native to South America. They are mainly found in the tributaries of rivers around Santa Elena in the Rio Tigre river and in the Rio Nanay in Peru. This species was first discovered in 2001 by Arendt and Paepke. In the wild, they move in shoals.


pencilfish appearance
Photo Credit: neryx, depositphotos

Like its name, this fish species has a long body with a sharp snout. They also have two horizontal black stripes across their red body.

If you observe it keenly, you’ll notice that the bottom half of the body appears paler than the rest. They also have a unique white spot at the bottom dorsal fin. Most pencil fish fish varieties have red, maroon, and orange coloration.


Like most species, the males and females are easy to differentiate. Males are paler than females. In addition, the males become brighter when they procreate. You’ll also notice a difference in their behavior; females appear more obedient.

Average Size

Pencilfish are nano fish species; therefore, they grow to about 1.5 to 2 inches as adults. They can survive for about five years. To keep them alive for this time, ensure that you source them from a reputable pet store.


Pencilfish are generally peaceful; therefore, they can comfortably live in a community tank. They can live as a single or together with other pencilfish species.

When adding them to an aquarium, keeping them in a group of 6 or more is advisable. Additionally, it would be best if you kept more females than males in the fish tank to prevent aggressive behaviors from the males. Because of their temperament, they are considered good tankmates.


When choosing tankmates for your pencil fish, remember that they should not be stocked together with larger and more aggressive species. Keeping them with such species could lead to them dying from hunger. Additionally, the bigger fish could treat them as food because of their size.

Some ideal tankmates for pencilfish include: tetras, barbs, rasboras, guppies, mollies, platies, Corydoras, swordtails, dwarf gouramis, and bristlenose plecos.

This fish variety easily gets stressed if you place them together with aggressive species.

Some of the bad tankmates for pencilfish are: tiger barbs, angelfish, oscars, and parrot fish because they grow bigger.

Tank Size and Conditions

Before keeping pencilfish, you must mimic their natural habitat in your aquarium. Unlike other fish varieties, the pencilfish is quite sensitive to changing environments.

They get irritated if you make sudden water changes or when the parameters get adjusted. Therefore, once you get them from the aquatic pet store, it’s advisable to acclimatize them first before placing them in the tank.

The ideal tank size for pencil fish is 20 to 30 gallons. They are quite active; therefore, they need a lot of space to swim. You’ll mostly find them at the top of the tank; therefore, you should cover the tank to keep them inside.

Since this fish variety likes clean water, you’ll need a filter to maintain the parameters and steady the water flow. Ensure you get the right filter for your tank according to the size of your aquarium. As you set up the tank, you need to add dark sand as a substrate.

You must also add floating plants because pencilfish love hiding in the tank. They also love resting in the driftwood decorations, so you should add them as well. Use plants with thin leaves to keep your fish happy. Maintain the water temperature between 72-78F and the pH at 5.7 to 7.


In the wild, pencilfish mostly feed on invertebrates and zooplankton. However, they can feed on anything in captivity since they are omnivores.

Pencilfish are not picky eaters making them ideal for beginners. As you plan their diet, you should include flake food, frozen food, dry products, and little pellets.

Additionally, you can treat pencilfish to live or frozen small animals like bloodworms and brine shrimps. Keep in mind that pencilfish have small mouths, so the food needs to be blended or smashed to prevent choking.

You should schedule the feeding times to one or two times a day to prevent overfeeding. Once they are done eating, remove the extra food from the tank to prevent contamination.


Aquarists have an easy time breeding pencilfish. To start the process, set up a separate 10-gallon tank and ensure that the water is warm with a gentle flow and dim lighting.

Add some males and females to the tank to start the breeding process. In addition, you need to add tons of dense foliage and Java moss to hide the eggs because pencilfish eat their eggs.

You should feed the active breeders live food for about a week. The female will lay about 25 to 30 eggs. The eggs usually hatch in about three to four days. Once the fry starts swimming, you can feed them micro worms and brine shrimp.


Pencilfish are popular because of their unique appearance. They are an ideal species for a community tank thanks to their size and peaceful nature. However, you must remember that they are quite sensitive to sudden changes as you stock them.


Jason Matthews

My name is Jason Matthews, and welcome to my website. When other kids were bragging about how their dog could sit and roll over, I was bragging about my latest Betta Fish and the cool sea castle I just added to his aquarium. 

Jason aquariume

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