Golden pencilfish Care Guide: Diet, Tank Mates, Diseases, Breeding & More

Updated: October 31, 2022

The golden pencilfish is a freshwater fish that is native to South America.

This fish is a peaceful community fish that does well in a tank with other peaceful fish. The golden pencilfish is a very small fish, reaching a maximum size of only 1.5 inches.

Despite their small size, they are a very active fish and do best in a tank with plenty of hiding places and a sandy substrate.

Species overview

Golden pencilfish (scientific name: Nannostomus unifasciatus) are a freshwater fish that’s found in the Amazon Basin of South America.

They occupy a wide range of habitats, from small creeks and streams to large rivers. However, they seem to prefer areas with a lot of vegetation and plenty of places to hide.

Golden pencilfish are very peaceful fish and do well in community tanks. They are also quite small, which makes them a good choice for nano aquariums.

One of the most unique things about golden pencilfish is their feeding habits. They are known to eat both live and frozen food, which is not common among most fish species.


Golden pencilfish

The Golden pencilfish is a freshwater fish that is native to South America. As the name suggests, these fish are a beautiful golden color.

The shade of gold can vary slightly from fish to fish but is usually a nice bright shade. This color is broken up by a black stripe that runs vertically down the length of the body.

The black stripe starts at the base of the operculum and extends all the way to the caudal peduncle.

Golden pencilfish have a long and slender body shape with a slightly pointed head. They have a dorsal fin that runs the length of their body and an anal fin that’s a bit shorter.

Their caudal fin is forked and extends out behind them. This fin is transparent with a black line running through the center.

Golden pencilfish also have a pair of barbels on their chin that they use to help them find food.


The lifespan of a golden pencilfish in captivity is between 3 and 5 years.

This is a relatively short lifespan when compared to other fish, but it’s still possible to extend their life by providing them with the best care possible.

Good water quality and a healthy diet are the two most important factors in keeping your golden pencilfish alive and healthy for as long as possible.


The Golden pencilfish is a small freshwater fish that only grows to be about 2.5 inches in length.


Tank Size

The recommended tank size for golden pencilfish is at least 20 gallons.

Even though they’re a small fish, they still need a fair amount of space to swim and feel comfortable. A 20 gallon tank is the minimum we recommend but if you can go larger, even by a few gallons, it will be much appreciated by your fish.

Water Parameters

The golden pencilfish is a tropical freshwater fish that needs warm water to survive. They’re found in the rivers and streams of South America, specifically in Brazil, Guyana, and Suriname.

In the wild, they prefer slow-moving water with plenty of vegetation. This provides hiding places and a consistent food source.

When it comes to water parameters, the golden pencilfish is relatively easy to care for. They prefer slightly acidic water that’s well-oxygenated.

Here are a few guidelines to help you create a healthy environment for your golden pencilfish.

  • Water temperature: 70 to 80 degrees Fahrenheit
  • pH levels: 6.0 to 7.5
  • Water hardness: 5 to 15 dGH
  • Alkalinity Levels: 2-12 dKH

What To Put In Their Tank

Golden pencilfish are a relatively small freshwater fish that come from South America.

In the wild, they inhabit slow-moving rivers and streams with dense vegetation. This is the type of environment you should try to recreate in their aquarium.

The first thing you need to do is choose a suitable substrate. These fish like to dig and forage around the bottom of the tank, so you’ll want something soft and sandy.

Next, you’ll need to add some plants. Golden pencilfish are shy by nature and will appreciate having plenty of places to hide.

We recommend using a mix of live and artificial plants. Live plants will help to oxygenate the water and provide a natural source of food, while artificial plants will last longer and be easier to keep in place.

Finally, you’ll need to add some driftwood or rocks. These fish like to have plenty of places to hide, so make sure you add enough to give them a sense of security.

Common Diseases

Golden pencilfish are a pretty hardy species, so they don’t often get sick. However, like all animals, they are susceptible to disease if they are kept in poor conditions or if they come in contact with a sick fish.

The most common disease that affects golden pencilfish is ich. This is a parasitic infection that manifests itself as white spots on the body of the fish.

If left untreated, ich can be deadly. However, it is fairly easy to treat if you catch it early.

Another disease that affects this species is hole-in-the-head disease. This is another parasitic infection, but it is much less common than ich.

This disease presents itself as pits or holes in the head of the fish. It is also fairly easy to treat if you catch it early, but it can leave permanent scarring.

The best way to prevent your golden pencilfish from getting sick is to maintain clean and stable water conditions in their tank. A healthy environment will go a long way in keeping your fish happy and disease-free.

Behavior & Temperament

The Golden pencilfish is a shy and reclusive fish that spends most of its time hiding in the plants at the bottom of the tank.

Even when they’re out in the open, they’re very timid and will quickly dart away if they feel threatened. Because of this, it’s best to keep Golden pencilfish with other peaceful fish that won’t bully them.

These fish are nocturnal, so you’re more likely to see them active at night. During the day, they’ll hide in the plants and only come out to eat when they feel safe.

Golden pencilfish are very sensitive to changes in their environment. They don’t do well with sudden changes in temperature, pH, or water hardness. Because of this, it’s important to acclimate them slowly to any new tank.

Overall, Golden pencilfish are peaceful and easy to care for as long as you provide them with a stable environment.

Tank Mates

Golden pencilfish are social creatures that do best in groups. In the wild, they’re often found in schools of several hundred individuals.

This is a good rule of thumb to follow when stocking your tank. A group of 6-8 is a good starting point, but you can go up from there if your tank is large enough.

As for tank mates, you have a few different options.

One is to choose fish that occupy different parts of the water column. This way, everyone has their own space and there’s less likelihood of conflict.

Another option is to choose fish that are similar in size. This is often a good strategy for avoiding aggression, but it’s not a guarantee.

Some compatible tank mates for golden pencilfish include:

  • Neon Tetras
  • Ember Tetras
  • Cardinal Tetras
  • Rummy Nose Tetras
  • Ghost Shrimp
  • Amano Shrimp
  • Cherry Shrimp


The golden pencilfish is a beautiful, easy-to-care-for fish that is well suited for the beginner fish keeper. They are a schooling fish that does best in groups of 5 or more of their own kind. They are peaceful and get along well with other small, peaceful fish.

Pencilfish are not difficult to breed in the home aquarium. They are egg-layers that scatter their eggs among plants, where the male will guard them until they hatch.

To induce spawning, it is best to set up a separate breeding tank. The breeding tank should be at least 10 gallons and have plenty of plants. The water should be soft and acidic with a temperature between 72-82 degrees Fahrenheit.

When the female is ready to lay her eggs, she will do so on the plants in the breeding tank. The male will then fertilize the eggs and guard them until they hatch.

It takes about 3-5 days for the eggs to hatch. The fry are very tiny and need to be fed micro worms or infusoria to survive.

As they grow, you can start to feed them baby brine shrimp or crushed flake food.


The Golden Pencilfish is a great fish for beginners and experienced aquarists alike. They’re easy to care for and don’t require a lot of special attention.

Even though they’re peaceful, they’re still interesting to watch and add a pop of color to your tank.

If you’re looking for a low-maintenance fish that’s still interesting and fun to watch, the Golden Pencilfish is a great choice!