Pencil Fish: Ultimate Care Guide

If you’re looking for species of fish that are unique and small but somewhat difficult to care for: consider the Pencil Fish. A Pencil Fish is actually the name of several different types of fish. Some types of Pencil Fish are the Golden Pencil Fish, Brown Pencil Fish, Purple Pencil Fish, Dwarf Pencil Fish, and several others. While most Pencil Fish are similar, some have different needs than others. Be sure to thoroughly research the specific type of Pencil Fish you plan on buying. Pencil Fish are all from the genus Nannostomus. Nannostomus comes from the Greek word for “Small Mouth.”

If you’re up for the challenge of caring for a Pencil Fish, then you’ve come to the right place. The first thing you’ll notice about a Pencil fish is its size. These petite fish grow to a max size of just over an inch or around 3 centimeters. Pencil Fish are not the easiest species to care for. Traditionally, the Pencil Fish has a slender body with a long horizontal black stripe running along it. Most species of Pencil Fish are endemic to South America and Africa. For example, the Cenepa Red Pencil Fish, the Coral Red Pencil Fish, the Hockey stick Pencil Fish, Purple Pencil Fish, and the Three-lined Pencil Fish are native to Peru.

Pencil Fish
Pencil Fish

Pencil Fish Care

The small size of the Pencil Fish may make them an appealing choice for most aquarists. However, it needs to be stated that caring for any fish, regardless of size or color or any other superficial feature, can be a daunting task. Every single species of fish has its own unique requirements. It is imperative that you do the required research before you even begin setting up the tank. Research and proper preparation can make even the most difficult fish a bit easier to own and care for. This is important because the Pencil Fish can be tricky to care for.

Are Pencil Fish Easy to Care for?

Pencil Fish are not easy to care for. Most experts would recommend having at least some experience in keeping fish before attempting to set up a tank for a Pencil Fish. Pencil Fish are very sensitive to their water quality and parameters. Most experienced aquarists tend to set up a quarantine to acclimate their Pencil Fish before them into their main tank. If you have a Pencil Fish, you should be sure to perform weekly water changes of around 25 to 50 percent. This will help keep the water clean, which in turn will help keep your Pencil Fish both happy and healthy.


Most Pencil Fish species are endemic to such locations as Africa and South America. A common thread between those three locations is their weather; they’re all considered warm locales. This obviously means that the Pencil Fish prefers warmer weather and temperatures. Following that line of thought would mean that your Pencil Fish requires warm temperatures in a tank setting. When setting up a tank for most Pencil Fish, you want the temperature to stay between 75 to 79 degrees Fahrenheit or 24 to 26 Degrees Celsius. That small range should be acceptable for most species of Pencil Fish, although certain species will be able to thrive in a wider temperature range.

An example of this is the Three-Lined Pencil Fish. The Three-Lined Pencil Fish can thrive in a temperature range between 75 to 82 degrees Fahrenheit. While this is a an average range that is acceptable for most Pencil Fish, there are some outliers such as the Cenepa Red Pencil Fish. The Cenepa Red Pencil Fish can thrive in temperatures as low as 64 degrees Fahrenheit, and as high as 82 degrees Fahrenheit. You’ll likely need a heater to achieve and maintain the warmer temperatures required by some Pencil Fish.

Water pH

While pH is an oft-overlooked water parameter for beginner Aquarists, that shouldn’t be the case for those aquarists setting up a tank for Pencil Fish. This is because Pencil Fish are not easy to care for and should be avoided by beginners. This means that anyone planning for a Pencil Fish will have the experience necessary to know how important the pH level is for any tank, not just a Pencil Fish tank. The pH level recommended for most Pencil Fish is 6.0 to 7.0. However, some species of Pencil Fish can thrive in a wider range of pH levels. The Golden Pencil Fish prefers a pH level of 5.5 to 8.0, while the Coral Red Pencil Fish can survive in a pH range of 4.0 to 7.0. While that is somewhat of a wide range, that does not mean you can neglect to check the pH level of the tank. As you know, any slight changes in pH can throw your entire tank out of sync and negatively impact every part of your tank. Routine checks of your pH level can ensure that you can find and remedy any changes to the pH level before they become a bigger and worse issue.

Pencil Fish Size

Simply put, the Pencil Fish is small, very small. Most fully grown Pencil Fish only averages around an inch and a half in length or 3.5 centimeters. That is, except for the Hockeystick Pencil Fish, which can grow to just over 5 centimeters or 2 inches. The largest Pencil Fish is believed to be the Black stripe Pencil Fish, which has a max length of over 2.7 inches. The smaller size of the Pencil Fish and their rich red color makes them appealing to countless people. This is because their small size makes them a perfect choice for a nano tank. The advantage of a nano tank is that they are small and can fit nearly anywhere. This makes the Pencil Fish a perfect choice for those experienced aquarists that are living in dorm rooms or small apartments. The size of a Pencil Fish also makes them an outstanding choice for a larger community tank; just be sure to research any potential tank mates beforehand.

Food and Diet

In the wild, the Pencil Fish tends to feed on small invertebrates as well as zooplankton. However, it is worth noting that the Pencil Fish is omnivorous, which means they will gladly eat both plant and animal matter. Pencil Fish being omnivorous means that they are easier to feed in a tank setting. When kept in a tank, a Pencil Fish will eat nearly anything, such as pellets, frozen food, dry food, cooked fish, or anything that’ll fit into its mouth. It must be noted that Pencil Fish have a small mouth, so you must be sure that you cut the food small enough for them to eat. It would help if you were to supplement the diet of your Pencil Fish with frozen or live bloodworms or brine shrimp.


When gauging the potential and expected lifespan of any pet, fish included, you need to realize that it’s not a guarantee. The lifespan of any fish or any pet depends on the care they are given. If you neglect any pet, its lifespan will very likely drop drastically. On average, the Pencil Fish lives for around 4 or 5 years. However, with proper care, proper maintenance, and a balanced diet, you might just be able to extend their lifespan. That is why it is imperative that you give any pet you have the best care that you can.

Tank Size

Tank size is an important parameter that you must consider before choosing a fish to add to your home. Pencil Fish are on the smaller side of the scale, measuring in at just over an inch. Due to the small size of nearly all types of Pencil Fish, they can be housed in a smaller tank. The small tank size required for a Pencil Fish means that you can put it nearly anywhere. The minimum tank size you should house a Pencil Fish is 10 gallons, even for the smallest species. If can keep your Pencil Fish in a larger tank, most experts recommend a 20 to 29-gallon tank. However, the larger tank size might preclude some people from owning a Pencil Fish.

Are Pencil Fish Schooling Fish?

Pencil Fish prefer to stay in groups of their own kind because they are a schooling species. If you plan on keeping your Pencil Fish together, you need them in a larger tank, usually around 20 to 29 gallons in size. You should keep around 8 to 10 Pencil fish in the same tank together. However, some types of Pencil Fish can be a bit aggressive toward each other. Because of this, you must ensure that you have more female fish than male, usually a 2-to-1 ratio. It is worth noting that having 8 to 10 Pencil Fish in the same tank can get a bit pricey. However, some reputable dealers will give a discount when buying certain fish species in bulk.

Tank Setup

A lid is one of the most important features you need to include in a Pencil Fish tank. Pencil Fish tend to be expert jumpers and will not hesitate to jump out of our tank if you leave it lidless. Plants are also a great option for a Pencil Fish tank. Because most kinds of Pencil Fish are endemic to extremely similar areas, you can set up their tank very similarly. Pencil Fish love to hide in and around decorations that you put in your tank. A darker substrate is also a great option for a Pencil Fish tank. You want a darker substrate because it will help the bright colors of the Pencil Fish to pop. You need to keep the pH level of your Pencil Fish tank between 5.7 to 7.0. The temperature of your Pencil fish tank should stay between 22 to 27 degrees Celsius or 72 to 78 degrees Fahrenheit.


Most experts can attest that breeding Pencil Fish isn’t a very difficult task. The most important part of breeding Pencil Fish is ensuring that your tank’s water is in the best condition possible. It would be best if you also had a separate tank specifically designed for breeding. Lighting is crucial in your breeding tank, as Pencil Fish don’t like harsh light. It would help if you used dim lights in a breeding tank. Your breeding tank’s temperature needs to be around 23 degrees Celcius, or 73 degrees Fahrenheit. As for pH, it should be just around 6.7. Keep in mind that male Pencil Fish may be slightly more aggressive toward other males during the breeding season. One of the most important aspects of breeding Pencil Fish is telling the difference between males and females. The easiest way to tell Pencil Fish apart is by their fins. The fins are the male Pencil Fish are much more brightly colored than their female counterparts.


Diseases can cause an issue for any fish kept in captivity. Pencil fish kept in captivity are more susceptible to certain diseases because of the stress that can be caused by adding things to the tank. Some diseases that Pencil Fish are susceptible are skin flukes, worms, protozoa, or other bacterial infections. The best way to keep your Pencil Fish happy is to prevent diseases.

Tank Mates

Before adding any fish to your tank, you must carefully research them to ensure they are compatible with Pencil Fish. Since Pencil Fish are a schooling species, the best tank mates are more of the same. Some other great options for Pencil Fish tank mates are Cherry Barbs, Tetras, Rasboras, and Mollies. You should avoid housing any Tiger Bars, Angelfish, or Oscars with your Pencil fish. Regardless of who or what you add to the tank, it would be best to quarantine them first. Quarantining them will help ensure your fish are not infected with any illness.

Where can I find Pencil Fish for sale?

Pencil Fish can be found online and locally in specialty aquarium stores. The price of Pencil Fish can vary depending on what type of Pencil Fish you purchase and where you purchase them from. They can go for as little as $3.99 or as much as $70. The Cenepa Red Pencil Fish can sell for anywhere between $30 to $64.99. While the Barred Pencil Fish goes for around $15. Then there is the Harrison Pencil Fish that can sell for as little as $3. The price of adding Pencil Fish to your tank can quickly balloon if you plan on adding an entire school.

Pencil Fish Species

There are many species of Pencil fish, and many of them are available in the aquarium trade. Here’s a list of some of the species of pencil fish:

  • Nannostomus anduzei
  • Nannostomus beckfordi (golden pencilfish)
  • Nannostomus bifasciatus (two-lined pencilfish, whiteside pencilfish)
  • Nannostomus britskii (spotstripe pencilfish)
  • Nannostomus digrammus (two-stripe pencilfish)
  • Nannostomus eques (brown pencilfish, diptail)
  • Nannostomus espei (Espe’s pencilfish, barred pencilfish)
  • Nannostomus grandis
  • Nannostomus harrisoni (Harrison’s pencilfish, blackstripe pencilfish)
  • Nannostomus limatus (elegant pencilfish)
  • Nannostomus marginatus (dwarf pencilfish)
  • Nannostomus marilynae (Marilyn’s pencilfish,greenstripe pencilfish)
  • Nannostomus minimus (least pencilfish)
  • Nannostomus mortenthaleri (coral-red pencilfish)
  • Nannostomus nigrotaeniatus
  • Nannostomus nitidus (shining pencilfish)
  • Nannostomus rubrocaudatus (purple pencilfish)
  • Nannostomus trifasciatus (three-stripe pencilfish)
  • Nannostomus unifasciatus (one-line pencilfish)

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