Cardinal Tetra
Paracheirodon axelrodi
The Cardinal Tetra exhibits vibrant blue iridescence and a distinct red stripe running along its body, making it a popular aquarium species.
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About the Cardinal Tetra
The Cardinal Tetra is a small, vibrant freshwater fish known for its striking iridescent blue and red coloring. It is closely related to the Neon Tetra but can be distinguished by the extended red stripe that runs the entire length of its body. People love keeping Cardinal Tetras in their tanks because they're peaceful and great at schooling together.
Quick Facts
Size
2 inches
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
20 gallons
Lifespan
4-5 years
Origin
South America
Diet
Omnivore - flakes, pellets, small live or frozen foods like brine shrimp and bloodworms
Water Parameters
23-27°C
4-6.5
5-12 dGH
Need a heater for this species?
This species needs 23-27°C in a 20 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Cardinal Tetras thrive in a well-planted aquarium with stable, soft to moderately soft, acidic water. Commonly recommended parameters are about 23-27°C (73-81°F) and pH roughly 4.5-7.0 (with softer, more acidic conditions often preferred).
- Keep water quality high by doing regular water changes and using a good filter, since Cardinal Tetras can be sensitive to ammonia and nitrite.
- Feed Cardinal Tetras a varied diet with high-quality flakes and add live or frozen foods like brine shrimp and daphnia for better health and color.
- Cardinal Tetras are schooling fish, so keep them in groups of six or more. They get along well with other small, peaceful species like corydoras and other tetras.
- Cardinal Tetras can be challenging to breed in home aquariums; they require specific water conditions, including very soft and acidic water, and dim lighting to encourage spawning.
- Be vigilant for signs of common problems like ich and fin rot, especially if water quality drops, since they can get sick quickly.
- Make sure the tank is covered because Cardinal Tetras can be jumpy and might leap out if scared, especially during water changes or if the lights come on suddenly.
Compatibility
Good Tankmates
- Small peaceful tetras such as Neon Tetras
- Peaceful rasboras like Harlequin Rasboras
- Small peaceful catfish like Corydoras
- Dwarf Gouramis
- Adult dwarf shrimp (with caution; may eat shrimplets)
- African Dwarf Frogs
Avoid
- Aggressive cichlids, such as Oscars
- Large angelfish (may prey on them)
- Fin-nippers like Tiger Barbs
- Bettas that may see tetras as competition
Habitat and Natural Environment
The Cardinal Tetra (Paracheirodon axelrodi) is native to the Orinoco and Rio Negro rivers in South America. These rivers are characterized by dark, tannin-rich waters with a sandy substrate and dense vegetation. The natural habitat of Cardinal Tetras often has subdued lighting due to overhanging canopies.
Tank Setup Requirements
To replicate their natural environment, a dark substrate and ample plant coverage are recommended for a Cardinal Tetra aquarium. Driftwood and leaf litter can also help mimic the soft, acidic conditions of their native waters.
- Tank size: Minimum 20 gallons for a small group.
- Water temperature: 73-81°F (23-27°C).
- pH level: 4.0 to 6.5.
- Lighting: Low to moderate.
Using an adjustable heater is essential to maintain stable water temperatures appropriate for Cardinals.
Feeding and Diet
Cardinal Tetras are omnivorous and thrive on a varied diet. They predominantly eat small live and frozen foods in their natural habitat, and this should be replicated as much as possible in captivity.
- High-quality flake food.
- Live or frozen brine shrimp.
- Daphnia.
- Bloodworms.
Feeding small amounts two to three times daily is better than a single large feeding.
Behavior and Temperament
Cardinal Tetras are peaceful fish that thrive in schools of 6 or more. They are social creatures that display their best colors and behaviors when kept with others of their kind.
They are ideal for community tanks with other non-aggressive species that thrive within similar water parameters.
Breeding
Breeding Cardinal Tetras in captivity can be challenging due to their specific needs. Successful breeding requires attentiveness to water conditions and often entails setting up a separate breeding tank with soft, acidic water.
- Dim lighting and spawning mop or moss for egg-laying.
- Maintain a temperature around 80°F (27°C).
- Condition breeders with a varied diet.
Remove adults after spawning to prevent them from eating the eggs.
Health and Common Issues
Cardinal Tetras are relatively hardy but require stable water conditions. They are susceptible to common freshwater diseases and stress-related illnesses.
- Maintain high water quality with regular changes.
- Watch for signs of Ich and fin rot.
- Avoid sudden changes in water conditions.
Quarantine new fish before adding them to a community tank to prevent the spread of diseases.
Similar Species
Other freshwater peaceful species you might be interested in.
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This is a tiny Panamanian livebearer that does best when you treat it more like a shy wild fish than a fancy guppy-lots of cover, calm vibes, and really clean water. The fun part is watching the males posture and spar while the females cruise around dropping fully-formed fry about once a month.
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Black neons are one of those little tetras that look kinda understated until the light hits them-then that bright stripe pops and they shimmer when the school turns together. They're super chill, always cruising mid-water, and they make a tank feel "alive" without being hectic. If you keep a nice group, they get bolder and you'll see way more of their personality.
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Black skirts are those little "suit-and-tie" tetras with the dark bands and flowing fins that look way fancier than they should for how tough they are. They're super active midwater fish, and when you keep a proper group they do that tight, zippy schooling thing that makes the whole tank feel alive. Just give them enough buddies and finny tankmates they won't be tempted to nip.
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