Cardinal Tetra


Common Name: Cardinal Tetra
Scientific Name: Paracheirodon axelrodi
Adult Size: 2 inches
Life Expectancy: 4-5 years
Tank Size: 10 gallons minimum

The Cardinal Tetra is a stunning freshwater fish, celebrated for its vibrant blue and red coloring that runs the length of its body. Native to the rivers of South America, these tetras are a favorite among aquarists for their schooling behavior and ability to add a splash of color to any aquarium.

A 10-gallon tank can house a small school of Cardinal Tetras, but larger tanks are preferable to give them more space to swim and display their natural schooling behavior. They are a peaceful species that does best in groups of six or more to help them feel secure and reduce stress.

Cardinal Tetras are omnivores and should be fed a varied diet of high-quality flake food, as well as frozen or live foods such as brine shrimp or daphnia to ensure proper nutrition. They are well-suited for community tanks with other peaceful, small fish species that share similar water parameters.

Origins and Natural Habitat

The Cardinal Tetra (Paracheirodon axelrodi) is a small and vibrant freshwater fish that is indigenous to South America. Your journey to understanding its origins would take you to the upper tributaries of the Orinoco and Negro Rivers. These areas span parts of Venezuela, Brazil, and Colombia. The natural habitat of these fish is characterized by soft, acidic waters. The acidity is a result of tannins released by decaying plant matter in these blackwater ecosystems.

In their native environment, Cardinal Tetras seek the shelter provided by the dense vegetation and fallen leaves that are abundant in these waterways. They are proficient at using these natural resources as hiding spots from predators. You will find that these habitats are rich in organic matter, which is instrumental in the diet of the Cardinal Tetra, contributing to their regular feeding habits.

Key Characteristics of Cardinal Tetra Habitats:

  • Location: Upper Orinoco and Negro Rivers in South America
  • Water Type: Soft and Acidic
  • pH Levels: Low due to tannins from decaying leaves
  • Vegetation: Dense, with an abundance of aquatic and land plant leaves

In your care, replicating these conditions is critical for maintaining the health of Cardinal Tetras. Therefore, understanding the origins and natural habitats of these fish is not just an academic exercise—it is essential knowledge for any aquarist interested in keeping Cardinal Tetras in a home aquarium setting.

Aquarium Setup

Setting up the appropriate aquarium environment is crucial for the health and longevity of Cardinal Tetras. They require a tank that replicates their natural habitat, with attention to tank size, environment, and specific water conditions.

Tank Size and Environment

Your aquarium should be at least 20 gallons to provide ample swimming space for your Cardinal Tetras. These fish thrive in schools, so a spacious tank allows for natural schooling behavior.

  • Minimum tank size: 20 gallons for a school of Cardinal Tetras
  • Preferred environment: Densely planted with hiding places and a dark substrate to mimic their natural habitat

Incorporate live plants such as Java moss and Anubias for coverage, enabling your fish to feel secure. Subdued lighting enhances the brilliant coloration of Cardinal Tetras, and driftwood or leaf litter can be added to simulate their rainforest streams.

Water Conditions and Parameters

Cardinal Tetras hail from soft, acidic waters, so replicating these conditions is essential for their well-being.

Parameter Value
pH level 5.0 – 7.0
Temperature 73°F – 81°F (23°C – 27°C)
General Hardness (dGH) < 8
Water change 25% weekly

Maintain a stable pH and avoid fluctuations to prevent stress. Use a reliable aquarium heater to keep the water temperature consistent, and consider a gentle filtration system to avoid strong currents while keeping the water clean.

Behavior and Social Dynamics

Cardinal Tetras display a peaceful and gregarious nature, often thriving in the presence of conspecifics. It is crucial for your shoal to consist of at least six individuals, which will help reduce stress and allow for their natural schooling behavior. A larger group, ideally around ten to twelve, is even more beneficial for maintaining a harmonious environment and dynamic social interactions.

Your observation will reveal that these fish engage in a more even-keeled swimming style when compared to some of their relatives. While they may not exhibit rigorous shoaling and darting, they are still active and often occupy the middle strata of the water column. Their adaptability to various tank conditions is remarkable, yet a stable environment that replicates their native habitat will best support their social structures.

When integrating Cardinal Tetras into a community aquarium, ensure their tank mates share a peaceful demeanor to preserve the calm social order. Aggressive or much larger fish can disrupt the tetras’ sense of security. By doing so, you’ll nurture their social interactions and witness the full extent of their collaborative and interactive behavior within the aquarium setting.

Compatibility and Community

When setting up a community aquarium, your choice of tank mates for Cardinal Tetras is crucial to maintaining harmony. These peaceful schooling fish thrive best with non-aggressive and similarly sized species. You’ll find that Cardinal Tetras coexist well with a range of community fish that share their preference for a calm environment.

Ideal Tank Mates for Cardinal Tetras:

  • Other Tetra Species: Such as Neon Tetras or Rummy-nose Tetras.
  • Dwarf Cichlids: Like Apistogrammas that are also peaceful in nature.
  • Livebearers: Guppies, Platies, and Mollies can be suitable if they are not too large or nippy.
  • Small Catfish: Corydoras and Otocinclus are good bottom-dwelling companions.
  • Shrimp & Snails: Amano shrimp, Cherry shrimp, and various non-aggressive snails.

To ensure your Cardinal Tetras feel secure and display their best behavior and colors, maintain a group of at least six, as they are schooling fish. Larger groups are even more effective in creating a serene atmosphere and reducing stress among individual fish.

Before introducing any new species to your tank, research their specific care requirements and confirm compatibility. This helps prevent aggression, stress, and potential disease. Remember, a spacious tank with plenty of hiding places and live plants will promote a healthy, dynamic community aquarium.

Health and Maintenance

Maintaining robust health in your Cardinal Tetras hinges on consistent cleaning and attention to disease prevention. Aquatic vitality is sustained through routine tank maintenance and a vigilant eye for signs of illness.

Cleaning and Maintenance Routines

To preserve the quality of your Cardinal Tetra’s environment, adhere to a regular cleaning schedule.

  • Weekly Tasks:
    • Water testing: Check the pH, ammonia, nitrite, and nitrate levels.
    • Partial water changes: Replace 25%-30% of the tank water to reduce harmful toxins.
  • Monthly Tasks:
    • Filter inspection: Clean or replace the filter media to ensure efficient operation.
    • Substrate cleaning: Use a gravel vacuum to remove food waste and debris.

Disease Prevention and Management

Prompt disease prevention can safeguard your fish from common health issues.

  • Quarantine new arrivals: Prevent disease introduction by isolating new fish for at least two weeks.
  • Balanced diet: Feed high-quality, varied foods to boost immune health.
  • Monitor for symptoms: Look for signs of stress or illness, such as changes in swimming patterns, discoloration, or lethargy.
  • Immediate isolation and treatment: If illness is suspected, isolate the affected fish and consult a veterinarian for diagnosis and treatment options.

Diet and Feeding

When feeding your Cardinal Tetras, focus on providing a varied diet that includes live, frozen, and dry foods to ensure balanced nutrition. The core of their diet in the wild consists of small insects, larvae, and crustaceans, which you can replicate with live foods like fruit flies and frozen fare such as bloodworms and daphnia.

For daily feeding, high-quality flakes or pellets should be your staple, as they are fortified with essential proteins and amino acids necessary for growth and vibrant coloration. It is important that these foods list fish meal, shrimp meal, or similar protein sources as their primary ingredients.

Your Cardinal Tetras will also benefit from occasional vegetarian food sources, such as spirulina, chopped algae, and blanched vegetables like lettuce, cucumber, and peas. This not only mimics their varied natural diet but also provides fiber and other important nutrients.

To avoid overfeeding, which can lead to health issues and tank pollution, feed your Cardinal Tetras small amounts two to three times a day. This should be only as much food as they can consume in three minutes. Consistent, varied, and measured feeding will ensure your fish remain healthy and vibrant.

Breeding and Reproduction

Breeding Cardinal Tetras successfully requires your understanding of their specific needs and behaviors. Your attentiveness to environmental details and the fishes’ lifecycle will greatly influence your breeding outcomes.

Gender Identification and Breeding Behavior

When preparing for breeding, identifying the gender of your Cardinal Tetras is crucial. Males are typically slimmer and more vibrant in color, while females tend to have a larger, more rounded belly, especially when they are full of eggs. Recognizing breeding behavior is also important; during courtship, males often display intensifying colors and perform intricate dances to attract females.

Creating Optimal Breeding Conditions

To simulate the natural breeding conditions of Cardinal Tetras, your aquarium should maintain water parameters within a specific range. Aim for a pH of 4.6 – 6.5water hardness between 2 – 6 dKH, and a temperature range of 73 – 81ºF (23 – 27ºC). Perform regular water changes, at least 25 – 30% weekly, to ensure the water quality remains high. Lighting should be similar to their natural habitat, which is often dim and diffused; consider using a daylight cycle with subdued lighting to mimic the shaded waters they originate from.

Growth, Development, and Lifespan

When you introduce a Cardinal Tetra (Paracheirodon axelrodi) into your aquarium, you are bringing in a small-sized species that will typically reach an adult size of 1.25 to 2 inches in length. Their growth rate is gradual, and they usually reach sexual maturity by about 8-10 months of age. It’s important for you to provide a stable and healthy environment to support their growth.

Your Cardinal Tetras will require proper care throughout their lives, which can span approximately 3 to 5 years. To achieve this lifespan, a well-maintained tank and a balanced diet are essential. Providing varied and nutrient-rich food contributes to their full development and longevity.

Table: Key Growth Stages of Cardinal Tetra

Age Range Size Developmental Stage
0-4 weeks < 0.5 inches Fry (juvenile)
2-4 months 0.5 – 1 inch Growing juvenile
8-10 months > 1 inch Sexual maturity reached
1-2 years 1.25 – 2 inches Adult

Remember to keep your school of Cardinal Tetras, ideally six or more, to promote a natural and stress-free environment. They thrive when social structure is respected, influencing both their growth and health positively.


Where Do Cardinal Tetras From?


What Is the Natural Habitat of a Cardinal Tetra?

With a vibrant display of colors and an enchanting demeanor, the Cardinal Tetra, scientifically known as Paracheirodon axelrodi, is a beautiful freshwater fish that originates from the soft, acidic waters of South America, particularly the upper Orinoco and Negro Rivers in Brazil, Colombia, and Venezuela. These regions provide a unique and richly biodiverse habitat that has shaped the needs and behavior of the Cardinal Tetra.

The natural environment of a Cardinal Tetra is characterized by slow-moving or still waters, with plenty of vegetation. These waters are typically dark, stained by tannins from fallen leaves and wood, creating a unique ‘blackwater’ condition that the Cardinal Tetras thrive in.


Being omnivorous, Cardinal Tetras have a diverse dietary regimen. They feed on a blend of brine shrimp, daphnia, and a wide range of high-quality flake foods. It’s crucial to remember to feed them in small portions but at multiple times throughout the day to maintain their health and vitality.


As schooling fish, Cardinal Tetras exhibit a preference for swimming in groups, showcasing interesting group dynamics. They generally maintain a peaceful demeanor and are non-aggressive, making them a perfect fit for community tanks with other peace-loving species.

Tank Setup

When setting up a tank for your Cardinal Tetras, strive to mimic their natural habitat as accurately as possible. This would involve incorporating a generous amount of aquatic vegetation, a dark substrate for the base, and a few hiding spots for them to retreat to. They are most comfortable in water temperatures ranging from approximately 73 to 81 degrees Fahrenheit.


Cardinal Tetras are known for their compatibility with most other peaceful fish species. Ideal tank mates for them include other species of Tetras, Guppies, and Corydoras. However, it is advised to avoid pairing them with larger, aggressive species that may view them as potential prey.


The process of breeding Cardinal Tetras can present certain challenges. They necessitate specific water conditions and require a separate breeding tank to be set up. During the breeding phase, the female will scatter her eggs amidst the plants, after which the male will fertilize them.


While Cardinal Tetras are generally robust and resistant, they can become prone to common fish diseases if their care and habitat maintenance are neglected. Frequent water changes, provision of a balanced diet, and careful monitoring of water parameters are integral to ensuring the health and vibrancy of your Cardinal Tetras.


What Do Cardinal Tetra Eat?


Are Cardinal Tetras Aggressive?

Tank Size

How Big of a Tank Does a Cardinal Tetra Need?


What Are the Best Tank Mates For Cardinal Tetras?


How Big Do Cardinal Tetras Get?