Cardinal Tetra Species Overview and Care Guide

cardinal tetra
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Last Updated: June 27, 2023 by Flora Gibbins

Did you know that the cardinal tetra is one of the most popular freshwater aquarium fish in the world? With its stunning iridescent blue and red colors, it’s no wonder that hobbyists of all experience levels are drawn to these little fish.

But beyond their beauty, cardinal tetras are also known for their peaceful nature and easy care requirements. In this guide, we’ll explore everything you need to know about keeping cardinal tetras happy and healthy in your own aquarium, from their origins in the Amazon rainforest to their ideal tank mates and diet.

So, let’s take a deep dive into the wonderful world of cardinal tetras!

Cardinal Tetra Facts and Overview

  • Common Names: Cardinal Tetra, Red Neon Tetra
  • Scientific Name: Paracheirodon axelrodi
  • Adult Size: 1.5-2 inches (3.8-5 cm)
  • Lifespan: 3-5 years
  • Colors and Markings: Vibrant red and blue — mostly red body, with a vibrant blue stripe running along sides.
  • Origin: Amazon River Basin, specifically the Negro and Orinoco River systems in South America.

But these quick facts barely scratch the surface of what makes Cardinal Tetras such a popular choice for aquarium enthusiasts. So let’s dive deeper into their appearance, behavior, care, and more!

Origin and Distribution

Cardinal tetras are native of the Amazon basin in South America, specifically in the small rivers that flow into the larger Rio Negro and Orinoco rivers in Colombia, Venezuela, and Brazil. These regions are known for their diverse and unique aquatic ecosystems, which are home to a wide variety of fish species.

The first recorded sighting of the cardinal tetra was by the renowned American aquarium fish importer, Herbert R. Axelrod during a trip to South America in the 1930s. He was struck by their stunning coloration and peaceful nature and decided to bring them back to the United States for aquarium enthusiasts.

The popularity of the cardinal tetra quickly grew, and they are now one of the most popular species in the aquarium trade.

Unfortunately, the demand for cardinal tetras has led to unsustainable fishing practices in some parts of their natural homes, which can impact wild populations. For this reason, it’s important to only buy cardinal tetras from reputable sources and to choose fish that have been sustainably sourced and ethically bred in captivity.

While they are mostly kept in home aquariums these days, cardinal tetras are still found in their native habitats throughout the Amazon basin. In the wild, they are typically found in slow-moving blackwater streams and flooded forest areas, where the water is soft and acidic, and the lighting is dim. They are often found schooling with other small fish species and can be spotted flitting among the vegetation and leaf litter on the riverbed.


The cardinal tetra is a small fish that typically grows to be around 1.5 inches long. What makes them so popular among aquarium enthusiasts is their stunning coloration, which features iridescent blue and red scales. The blue coloration runs from the head to the midsection of the fish, while the lower half is bright red. They also have a small, iridescent blue spot just behind their eyes.

But it’s not just the colors that make them unique – the cardinal tetra also has a distinctive black “line” that runs from the nose to the tail. This black line, also known as the “band,” is what helps to distinguish them from other similar-looking tetra species.

In addition to their vibrant colors, cardinal tetras also have long, flowing fins that add to their graceful appearance. Their dorsal fin, which runs along the top of their body, is tall and pointed, while their anal fin, which is located on the bottom of their body, is more rounded.

Behavior and Temperament

Cardinal tetras are known for their peaceful nature and are often kept in community aquariums with other small, non-aggressive fish. They are schooling fish, which means they thrive when kept in groups of six or more. When kept in schools, they feel safer and are more likely to display their natural behavior, such as darting and swimming together in synchronized movements.

As mentioned earlier, cardinal tetras are native to dimly lit environments, and they prefer aquariums that are not too bright. In fact, they can become stressed and even lose their vibrant colors if kept in bright lighting for extended periods. It’s important to provide them with plenty of hiding places, such as plants or driftwood, where they can retreat when they feel the need to.

One of the most interesting behaviors of the cardinal tetra is their ability to communicate with one another through flashing. Flashing is when the fish quickly and briefly display their bright colors as a way to communicate with other members of their school. This behavior is thought to help maintain group cohesion and warn other fish of potential threats.

Cardinal Tetra Tank Mates

When choosing tank mates for your cardinal tetras, it’s important to select fish that are peaceful and won’t bully or attack them. Cardinal tetras are small and delicate, so they can be vulnerable to larger or more aggressive fish. Here are some tips for choosing compatible tank mates for your cardinal tetras:

Compatible Fish Species

Some good options for tank mates include other small, peaceful fish such as other types of tetras, rasboras, and small corydoras catfish. Guppies, mollies, and other livebearers can also make good tank mates, as long as they are not overly aggressive.

How Many Can Be Kept Together?

As schooling fish, cardinal tetras thrive in groups of six or more, so it’s important to keep this in mind when selecting tank mates. Aim to keep at least six cardinal tetras together, and consider adding other compatible species in groups of at least three to four.

Tank Mates to Avoid

Avoid keeping cardinal tetras with larger or more aggressive fish such as cichlids or larger catfish. They may see the small tetras as food or become aggressive towards them. Avoid keeping them with fin-nipping species like some barbs and danios as well.

It’s also important to note that cardinal tetras are sensitive to changes in water parameters, so it’s important to monitor your tank’s water quality regularly and avoid adding any fish that may cause a significant increase in waste or pollution.

By choosing compatible tank mates for your cardinal tetras, you can create a peaceful and harmonious aquarium community that will be a joy to watch and care for.

cardinal tetras in aquarium

Cardinal Tetra Care

Proper care is essential for keeping your cardinal tetras healthy and happy in your aquarium. Fortunately, cardinal tetras are relatively easy to care for and don’t require any special equipment or advanced knowledge.

In this section, we’ll cover the basics of cardinal tetra care, including tank setup, water parameters, and diet. With a little bit of effort and attention, you can provide your cardinal tetras with a comfortable and thriving environment that they’ll love to call home.

Tank Setup

Setting up the perfect environment for your cardinal tetras is crucial to their long-term health and well-being. Here are some important factors to consider when setting up their tank:

Tank Size

The general rule of thumb is to provide at least 2.5 gallons of water per fish, which means a minimum tank size of 15 gallons is recommended for a school of six cardinal tetras.

However, it’s important to note that this is a minimum recommendation, and a larger tank would be even better. A larger tank provides more swimming space for the fish and helps to dilute waste and pollutants in the water, leading to a healthier and more stable environment for your fish.

If you want to add more cardinal tetras to your tank, you’ll need to adjust the size of your tank accordingly. For example, if you want to keep a school of 12 cardinal tetras, you would need a minimum tank size of 30 gallons.

When adding other compatible species to the tank, you’ll also need to adjust the tank size based on the needs of the additional fish. Aim to provide at least 2 gallons of water per inch of fish, but keep in mind that some species may require more space than others.

It’s important to do your research and make sure that the fish you’re adding to your tank are compatible not only in terms of temperament but also in terms of tank size and water quality requirements. A well-planned and properly stocked aquarium can be a beautiful and rewarding addition to your home, but it requires careful consideration and attention to detail to ensure the health and happiness of your fish.

What to Put In Their Tank

Cardinal tetras enjoy a planted tank with plenty of hiding spots such as rocks, caves, and driftwood. Live plants such as Java moss, Java fern, and Amazon sword not only provide hiding spots but also help to maintain water quality by absorbing nitrates and other waste products.


A good filtration system is essential to maintaining good water quality and keeping your fish healthy. A filter should be able to turn over the entire volume of your tank’s water at least 5 times per hour.


When it comes to substrate, cardinal tetras prefer a soft, fine-grained substrate such as sand or gravel. Avoid using rough or sharp substrate materials that could damage their delicate fins.

Water Parameters

Maintaining proper water parameters is essential for keeping your cardinal tetras healthy and happy. In their natural habitat, they are used to soft, acidic water with a pH range of 4.0 to 7.0. To replicate these conditions in your aquarium, here are some important factors to consider:

  • Temperature: 72-82°F, with 78°F being the ideal temperature
  • pH Level: 4.0 to 7.0.
  • Hardness: Range of 1-10 dGH. They can tolerate slightly harder water as long as the pH is within their preferred range

Regular water changes are essential for maintaining good water quality in your tank. Aim to change 20-25% of your tank’s water every week to keep the water clean and healthy for your fish.

If you’re unsure about the water quality in your tank, consider using a water testing kit to monitor the pH, temperature, and other important parameters on a regular basis.

Diet and Feeding

Cardinal tetras are omnivores, which means they eat both plant and animal matter. In the wild, they primarily feed on small insects and zooplankton. In captivity, it’s important to provide them with a balanced diet that meets their nutritional needs. Here are some tips for feeding your cardinal tetras:

  • Feed your cardinal tetras small amounts two to three times a day, only as much as they can eat in about two to three minutes per feeding.
  • Provide a varied diet to ensure they are getting all the necessary nutrients, including:
    • High-quality commercial flake or pellet foods formulated for small tropical fish
    • Live and frozen foods such as bloodworms, brine shrimp, and daphnia (fed occasionally)
    • Boiled and cooled vegetables such as spinach or zucchini (fed occasionally)
  • Choose appropriately sized foods for their small mouths to avoid overfeeding and polluting the water.

Common Diseases

Like any other fish, cardinal tetras are susceptible to certain diseases and health issues. Here are some of the most common diseases that can affect cardinal tetras:


Ich is a common parasite that can affect many types of fish, including cardinal tetras. Symptoms include white spots on the fish’s body, increased scratching or rubbing against objects in the tank, and lethargy. Treatment involves raising the temperature of the tank and adding a medication specifically designed to treat ich.

Fin Rot

Fin rot is a bacterial infection that can cause the fins of cardinal tetras to become frayed or discolored. This can be caused by poor water quality, stress, or a weakened immune system. Treatment involves improving water quality, removing any infected or dead tissue, and adding an antibiotic medication.


Velvet is a parasitic disease that can cause a yellowish or gold dust-like coating on the fish’s body. Symptoms may also include lethargy, loss of appetite, and rubbing against objects in the tank. Treatment involves raising the temperature of the tank and adding a medication designed to treat velvet.


Columnaris is a bacterial infection that can cause cotton-like growths on the fish’s body, as well as redness and inflammation. Treatment involves improving water quality, removing any infected or dead tissue, and adding an antibiotic medication.

Preventing diseases in your cardinal tetras involves maintaining good water quality, avoiding overcrowding, and providing a balanced diet. Be sure to observe your fish regularly and look out for any signs of illness.

Breeding Cardinal Tetras

Breeding cardinal tetras can be a fun and rewarding experience for aquarium hobbyists. Here are some tips for successfully breeding these colorful fish:

Gender Differences

Distinguishing between male and female cardinal tetras can be challenging, but there are some subtle differences to look out for. Females tend to have a rounder belly, while males are slimmer and more streamlined. During breeding season, males may also exhibit brighter colors and more prominent red stripes.

The Breeding Process

Cardinal tetras are egg scatterers, meaning they release their eggs and sperm into the water for fertilization. To encourage breeding, you can create a separate breeding tank with a gentle filter and a spawning mop or mesh. You can also condition your fish by feeding them a variety of high-quality foods and gradually increasing the temperature of the water.

Once your fish are ready to breed, the female will scatter her eggs over the spawning mop or mesh, and the male will release his sperm to fertilize them. After a few days, the eggs will hatch into fry, which can be fed on a diet of infusoria or newly hatched brine shrimp.

Breeding Tips

Here are some pointers to increase your chances of success:

  • Provide a separate breeding tank with a gentle filter and a spawning mop or mesh.
  • Keep the breeding tank dark and quiet to reduce stress on the fish.
  • Monitor the water quality and perform frequent water changes to maintain good water conditions.
  • Use a heater to maintain a stable temperature in the breeding tank.
  • Provide plenty of hiding spots and plants in the breeding tank to give the female a place to lay her eggs.
  • Consider adding a breeding cone or slate to the breeding tank, which can help to attract the fish and provide a surface for egg laying.
  • Remove the adult fish from the breeding tank once the eggs have been laid to prevent them from eating the eggs or fry.
  • Be patient and don’t rush the breeding process. Cardinal tetras may take some time to condition and may not breed successfully on the first attempt.

Related Species

Here are some other popular tetra species that are related to cardinal tetras:

These tetra species have similar care requirements to cardinal tetras and can make great additions to a community aquarium. However, it’s important to research each species thoroughly and ensure that they are compatible with your current tank setup and other fish species.

FAQs on Cardinal Tetras

Are cardinal tetras suitable for beginners?

While cardinal tetras are relatively easy to care for, they can be more sensitive to changes in water quality and other stressors compared to other beginner fish. As such, they may not be the best choice for complete beginners.

Do cardinal tetras need a heater?

Probably, cardinal tetras are tropical fish and require a consistent temperature between 72-82°F to thrive. Unless you live in the tropics, a heater may be needed for maintaining the proper temperature in their tank.

Do cardinal tetras jump out of the tank?

Cardinal tetras are not known to be strong jumpers, but it’s always a good idea to provide a secure lid or cover for their tank to prevent any accidental escapes.

Are Cardinal Tetras for You?

Before adding Cardinals your tank, it’s important to consider whether they are the right choice for you and your setup.

If you’ve considered your tank size, the fish you currently own, the extra time and money that you’ll need to set aside for a new addition, and ultimately decided that cardinal tetras are a good fit for you and your aquarium, they can be a wonderful addition to your tank. With their striking colors, peaceful temperament, and fascinating behavior, cardinal tetras are sure to bring joy and beauty to any community aquarium.

Cover Image: User:Lerdsuwa, CC BY-SA 3.0, via Wikimedia Commons

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