Cardinal Tetra (Red Neon Tetra): Diet, Habitat, Compatibility & Breeding

The Cardinal tetra is a beautiful addition to a planted aquarium. In a school, the Cardinals with iridescent horizontal stripes, provide a breathtaking spectacle that can vitalize any aquarium. Moreover, Cardinal tetra care is relatively simple and accessible to even the newest to the hobby.

Cardinals are endemic to soft tropical freshwater habitats in Brazil, Venezuela, and Columbia. As one of the most popular fish in the fishkeeping hobby, they are widely available in most local fish stores.

Cardinal tetras live relatively long lives, generally between 2 to 4 years.


The scientific name of Cardinal tetras is Paracheirodon axelrodi. Para in Greek stands for “related to” and Cheirodon refers to a genus different from that of the Cardinal. Axelrodi refers to the family name of author Herbert R. Axelrod, who was the author and publisher of numerous pet care books.

Cardinal tetras are also known as the Red Neon tetra.


The cardinal tetra is brilliantly colorful. Its most distinguishable features are its iridescent blue and brilliant red lines on the ventral parts. The dorsal, pectoral, pelvic fin and anal fin of the cardinal tetras are generally transparent.

Cardinals are schooling fish and as such, provide a beautiful sight as they swim across the aquarium in unison.

The appearance of the Cardinal tetra is similar to the Neon tetra, which is are also very common in the hobby. Neon tetras are generally smaller and not as colorful as cardinals. However, they are remarkably similar are fishkeepers oftentimes confuse them.

Cardinals depict sexual dimorphism, which means that males and females will have different appearances. In the case of female Cardinals, they are generally larger and rounder than males when they reach sexual maturity.

Mature Cardinals will generally be 2-3 centimeters in size, (.80 to 1.20 inches).

Habitat & Tank Condition

Cardinals in the wild are generally found in blackwater or clearwater streams, which are heavily planted with a stony floor ground. Due to their size and peaceful nature, the fish prefers shaded and sheltered environments.

Temperature20 to 28 CelciusSpecific GravityFreshwaterTank Size10 Gallons +
pH5 to 7Level of Hardness5-19 °d

The pH of your aquarium should range between 6.5 and 7.5. Cardinal tetras prefer slightly acidic water, which can be achieved with botanicals, such as Indian almond leaves, blackwater extracts, pH buffering products, peat moss, and driftwood.

Water hardness should be between 0.5 and 2 dGH.

Cardinals are tropical fish, from South America. It is therefore recommended that you house your fish in an aquarium whose temperatures range between 22 and 26 degrees Celsius (72 to 80 Fahrenheit). Depending on your location, you will need to equip your aquarium with a heating unit.

EHEIM heater

If you live in colder climates, an adequate heater is the EHEIM Jäger TruTemp, which I prefer due to its precise accuracy and durability. Other notable brands include Fluval and Aqueon.

To remove harmful chemicals from your aquarium, like nitrates, it recommended that you use a filter.


Cardinal tetras will eat a variety of foods. As omnivores, they will eat both fibrous foods and protein. Providing a varied diet is important because it ensures that your tetras get all their essential nutrients.

You can feed your Cardinals dry foods like granules, flakes, wafers, crisp, and pellets. For protein, live or freeze-dried foods are a good choice, including bloodworms, daphnia, brine shrimp, infusoria, earthworm, and tubifex.


Cardinal tetras are small fish, so make sure that the food you give them is small enough to enter their mouth. For example, I always break up flakes into tiny little pieces, to almost powder. My Cardinals seem to struggle a lot less with their food. If you have fry, this is especially important, as their mouth may not be big enough to eat certain foods.

Give your tetras enough food to feed them for less than 5 minutes. If after 5 minutes of feeding your fish are not done eating everything, then that a sign that you have given them too much food. Overfeeding can lead to serious issues, like illness and polluted water, so you should always aim to feed just the right amount of food.


As mentioned earlier, Cardinal tetras are schooling fish, who prefers to be in a group of 6 or more. They are quite peaceful and make a brilliant addition to a community tank. You may be able to pair these fish with betta fish, who tend to be more aggressive.

Tetras, for the most part, have an unthreatening appearance to other fish, even the Betta splenden, who will not be bothered to fight these. However, this may not always be the case. To increase safety, adding more tetras to the mix may even further deter the splendens aggressivity.


Breeding Cardinal Tetras in a home aquarium can be difficult. The species can be fickle and may not always breed even when the parameters are set right.

To breed Cardinals, it is best to have the parents alone in the aquarium. Dim lighting is especially important during breeding, as this will ease the parents. In the wild, this is important as the parents seek refuge for their eggs from other predatory fish. The waters pH should be slightly acidic, between the range of 5.5 to 6. Water hardness should be low, between 0.5 to 1.5 dGH.

When introducing the breeding pair into the aquarium, the light should stay turned off. As the days go by, slightly increase the amount of lighting. Soon enough, the pair will breed and spawn their eggs.

Cardinal tetras are oviparous and can up to 100 eggs in one spawn. The eggs are adhesive, which means that they will glue to rocks and plants.

Once the eggs are spawned, it then recommended to remove the parents, as the parents oftentimes eat the eggs.

The eggs of Cardinals will hatch 24 to 36 hours later and generally provide between 25 to 50 offspring.

Dim lighting is important even after the eggs are spawned. The eggs and fry are extremely sensitive to lighting,

Once the fish have hatched, make sure to fish them with small foods like infusoria or dry fry foods.

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