Penguin Tetra: Species Overview

Category: Tetra

Common Names: Penguin Tetra

Scientific Name: Thayeria boehlkei

Family: Characidae

Minimum Tank Size: 20 Gallons

Care Level: Easy

Temperament: Peaceful

Max Size: 1 ½ Inches

Temperature: 72-80 F

pH: 6.0-8.0

Tank Level: Middle to Top

Colors: Yellow, Black

Diet: Omnivore

Breeding: Moderate

Penguin Tetra in Front of Plants

Penguin Tetra: Species Overview

Penguin Tetras are playful fish with a unique semi-upright swimming style, making them a popular choice for freshwater tanks. They get along well with other tank mates of similar sizes as long as you purchase multiple fish so they can school.

Since penguin tetras are easygoing on their tank parameter requirements, they’re excellent fish for beginner fish keepers.

That said, penguin tetras have limits on the water conditions they can tolerate. So, it’s crucial to set up their tank and water correctly to maximize their longevity.

Distinguishing Features

You might have to get a little creative at first to view the penguin tetra as having penguin-like qualities. But the combination of silver and black coloring with their semi-upright swim style eventually turns many disbelievers into believers.

Penguin tetras have a white or olive body as a base. They then have a single, thick black stripe that runs from the back of their eye down the middle of their stomach and to the bottom end of their tail.

Adding to the uniqueness of penguin tetras is the fact that they have a see-through silver belly.

Although penguin tetras have a traditional fish appearance with standard-sized fins, a slender body, and a forked tail, their swimming behavior separates them from most other fish. They have a sem-upright swim style.

Since penguin tetras are schooling fish, it’s a delight to watch groups of them swim together in a tank.


Penguin tetras originate from the Amazon River and its tributaries in South America.

They enjoy cloudy freshwater, as they live in areas with a lot of decaying plant matter. Heavy rains and flooding in the Amazon River also mean penguin tetras frequently encounter muddy conditions.

Since penguin tetras usually stay in the middle to the upper portion of the water column in the wild, they don’t often make their way to the mud and sand substrate.

They’re not big herbivores, although they’ll pick at algae and other plants in their environment. Many aquatic plants live in the Amazon river, including the water hyacinth, Amazon sword plant, and Salvinia.


Penguin tetras grow anywhere from 1.5 to 3 inches long in captivity. However, it’s more common for them to remain in the 1.5 to 2.5-inch range.

Nevertheless, penguin tetras are one of the largest types of tetras.

There’s little difference in length between male and female penguin tetras. But females have a girthier appearance around their stomachs compared to males.


Penguin tetras live up to five years in captivity, which is longer than their average lifespan in the wild. You can expect your fish to live at least three years as long as you provide them with the proper living conditions.

Maintaining the proper tank parameters is one of the best things you can do to improve the longevity potential of your penguin tetras.

You should also ensure that your fish live in groups so that they can socialize and school. Providing them with enough swimming space is also vital for their longevity, as it reduces stress.


It’s nearly impossible for the untrained eye to tell if you have a female or male penguin tetra if there’s only one gender in the tank.

However, male penguin tetras have brighter silver, olive, and black colors than females. They’re also thinner.

In contrast, females have duller colors and a rounder belly. But it isn’t until they’re ready to spawn and their bellies fill with eggs that you can easily tell the difference in genders from size alone.


Penguin tetras are social fish that are usually peaceful. Keeping them in groups of five or more is vital so that they can interact with each other.

Otherwise, if your penguin tetras don’t have enough companions of the same species, they may nip the fins of other tank mates.

But overall, fish keepers feel comfortable housing penguin tetras with other fish of a similar size.

Most of the time, male and female penguin tetras are equally peaceful fish. But when it’s mating time, it’s common to see males turn more aggressive.

These males often chase females around the tank, trying to showcase their worthiness as mating partners.

Juan R. Lascorz [CC BY-SA 3.0]

Tank Parameters

Knowing the correct tank parameters for penguin tetras is vital before bringing these fish home. Below are the most important aspects to consider.

Minimum Tank Size

You should purchase a minimum 20-gallon tank that’s at least 24 inches long for every five penguin tetras you want to have.

But the larger the tank, the happier your fish will be. So, we recommend aiming for a 30-gallon tank per five fish if your budget and space in your home allow for it.

Water Parameters

Once you buy your tank, it’s time to add water and achieve the following conditions before adding your penguin tetras.


Penguin tetras enjoy warm water between 72°F to 82°F.

Using a heater and thermometer to ensure the water temperature remains within this range is crucial to your fish’s health.


High tolerance for ranging pH levels is iconic of the penguin tetra. As long as their pH is between 6.0 to 8.0, they’ll be happy.

As with all the water parameters we’re covering here, aiming for the middle of the range is ideal. That way, should the conditions increase or decrease some, your penguin tetras will still be able to live well.


Penguin tetras are freshwater fish, so they don’t need salt in their aquarium. In fact, putting them in a saltwater tank will kill them.

Nevertheless, small amounts of aquarium salt can sometimes benefit tropical fish. Salt has immune-boosting benefits and can help kill certain types of parasites, bacteria, and fungi.

So, if you notice that your penguin tetras are looking unwell, adding some aquarium salt to their tank and performing a partial water change may be beneficial.

Tank Setup

Now that you have the right water parameters, the fun begins with setting up your penguin tetras tank. But before you pack their aquarium full of castles and other fun decorations you find online, keep the following in mind.


Penguin tetras aren’t picky about their substrate since they rarely visit it.

So, feel free to choose whatever sand or smell pebble bottom you’d like for your tank.


Decorations aren’t essential for penguin tetras as long as you place plants in the tank, which we’ll cover next.

However, adding a piece or two of floating driftwood can be an excellent way to mimic their natural environment. You can also add decorations that reach the middle of the tank or higher so your penguin tetras can use them for playing and hiding spaces.


Plants are vital to penguin tetras for two reasons—they use them for hiding spaces and to avoid bright tank lights, should you need a bright light for other fish species in the aquarium.

Penguin tetras live in densely vegetated areas. Therefore, you should select plants that grow both from the bottom up and float on top of the water with roots that hang down.

Some excellent plants to place in a penguin tetra tank include:

  • Water wisteria
  • Java fern
  • Red root floater
  • Dwarf water lettuce

While it’s essential to offer your penguin tetras lots of vegetation, be sure also to leave open space so these fish can swim freely.


Penguin tetras don’t like a lot of light.

These fish live in murky water in the wild. Plus, the densely vegetated areas they live within mean that plants block out a lot of sunlight.

Therefore, it’s best to have an aquarium light on a dim setting. If you need a brighter light because of other fish in the tank, it’s vital to keep a portion of the tank densely vegetated so your penguin tetras can escape it.


Ammonia, nitrogen, and other toxins will build up in your penguin tetra’s tank without a filter since it’s a closed system.

Therefore, you should choose a high-quality filter compatible with the size tank you purchase. Ideally, your filter should provide a light water flow, mimicking the penguin tetra’s natural habitat.


Since penguin tetras like their water so warm, installing an aquarium heater is a must.

Be sure also to purchase a thermometer. You can place the thermometer on the side of the tank, offering an efficient way to check the water temperature whenever you feed your fish.


Penguin tetras are omnivores, but they tend to eat more carnivorous foods. They’ll eat insects, worms, and water larvae in the wild.

It’s important to give your penguin tetras a varied diet to keep them in optimal health. Some excellent foods include:

  • Bloodworms
  • Brine shrimp
  • Algae wafers
  • Tubifex
  • Fish flakes
  • Fish pellets

You should feed your penguin tetras twice per day. Let them eat as much as they can in three minutes.

Then, remove the remaining food so that it doesn’t spoil in the tank.


Breeding penguin tetras is easy, but you’ll need a separate breeding tank.

To encourage your fish to get ready to spawn, give them a protein-rich diet via live foods. You should also change the pH to be more acidic (6.0 – 6.9).

The males will begin chasing the females around the tank when they’re ready to spawn. Likewise, the females will start getting fatter as they grow eggs.

Once the female releases her eggs and the male fertilizes them, move the fish back into their original tank. Otherwise, the parents may eat the eggs.

A single penguin tetra can lay as many as 1,000 eggs. The eggs will hatch within 24 hours, and you can expect the fry (baby penguin tetras) to grow up to one inch in their first month.

Common Diseases

You can prevent many diseases in penguin tetras by regularly changing the tank water, following the parameters we discussed, and ensuring your fish have enough space in their tank.

But inevitably, some diseases can still impact your fish. Below are some of the most common illnesses your penguin tetra may develop.

Neon Tetra Disease

Neon tetra disease is a fatal and highly contagious condition caused by parasites. It passes among fish, particularly when penguin tetras pick at dead fish or food that contains the parasite.

Signs that your penguin tetra has neon tetra disease are the development of cysts, loss of color, and difficulty swimming.

Sadly, it isn’t possible to cure neon tetra disease. So, preventing it from arriving in your tank is vital.


Ich is another common parasitic infection in penguin tetras. It passes between other infected fish, and its larvae can live on the substrate for a long time without a host.

Spotting ich is easy, given that your penguin tetra will develop small salt-like spots on its body. They’ll also scratch against hard surfaces.

You can treat ich by applying ich medicine to the water and changing the water frequently.

Gill and Skin Flukes

Gill and skin flukes are technically two different parasites—dactylogyrus and gyrodactylus.

But they have similar symptoms in penguin tetras, including eating the gills and skin, causing clamped fins, and increasing mucus production.

You can manage fluke infestations by adding aquarium salt to your tank and a medication aimed at killing these parasites.

Potential Tank Mates

Many tank mates are suitable for penguin tetras, given that these are typically peaceful fish. It’s even common for them to interact with other schooling fish that are of a similar size.

That said, it’s vital to avoid placing fish with long fins in the tank, as penguin tetras may nip at them. Penguin tetras may also become food for larger fish, so be mindful of their tank mates’ sizes.

Some of the best tank mates for penguin tetras include:

  • Kuhli loaches
  • Cherry barbs
  • Buenos Aires tetras
  • Corydoras
  • Red tail sharks
  • Silvertip tetras

And this list is just a few of the many excellent options. But before you add tank mates of other species to your penguin tetra’s tank, be sure to put a minimum of five penguin tetras together.