Paracheirodon axelrodi (Cardinal Tetra Fish)

Paracheirodon axelrodi

Last updated on August 30th, 2022 at 02:55 pm

The cardinal tetra fish, also known as Paracheirodon axelrodi, originates from the Amazon River basin of South America and was one of the earliest fish to be bred in captivity. It has been found in the blackwater tributaries of the Rio Negro and in some rivulets in the Solimões (upper Amazon) basin in Brazil, Colombia, Peru, Ecuador, and Bolivia. The species was named after Swedish aquarium fish collector Carl-Herman Axelrod.

The Cardinal Tetra, Paracheirodon axelrodi, has been gaining popularity in the aquarium trade in recent years due to its attractive red, blue, and black coloration and ease of care. This hardy fish requires minimal care, comes in a wide variety of vibrant colors, and can live peacefully with other species in both freshwater and saltwater aquariums.

A popular fish in the aquarium hobby, Paracheirodon axelrodi, is just one of many species of beautiful tropical freshwater fish that can be found on the lowland rainforest streams of South America. In this article, you’ll learn more about the cardinal tetra and what to expect if you’re thinking about adding one or more to your home aquarium!

Origin and descriptions

Paracheirodon axelrodi

Paracheirodon axelrodi (popularly known as cardinal tetra) is a freshwater tropical fish belonging to the characin (characidae) family. It belongs to the genus Paracheirodon and the order Characiformes. It was first described by Schultz in 1956 from northern Guyana and named Paracheirodon axelrodi in honor of Dr. Axelrod who helped in the collection of fishes from these locations.

The type specimen was collected from Potaro River at Georgetown, Guyana. Paracheirodon axelrodi can be distinguished easily by their colours and they are one of most popular aquarium fishes all over the world due to their vivid coloration. They are native to South America where they can be found in Essequibo, Takutu, and Courantyne river basins of Guayana Shield in Venezuela, Brazil, Colombia and Ecuador. They inhabit slow-moving blackwater tributaries and flooded forests.

Species profile

Paracheirodon axelrodi

Paracheirodon axelrodi (the cardinal tetra) is a freshwater aquarium fish from South America that can also be found in some pet stores in North America. It is one of three species of Paracheirodon. Paracheirodon axelrodi is arguably the most popular and easiest to find in many stores and online retailers throughout North America because it’s hardy and easy to care for.

Smallmouth Bass Fish

Another reason why it’s so common is that they are beautiful fish and easy on the eyes. The cardinal tetra comes in bright red and blue, with black stripes. They are small at around 2 inches but have a long lifespan – about 7 years. As omnivores, they should eat a variety of foods such as flake food or pellets, vegetables, or frozen foods like bloodworms.

Water conditions should be soft and acidic at around pH 6-7 with high levels of oxygenation due to their active swimming behavior; low oxygenation can lead to fin rot and tail rot quickly.

Paracheirodon axelrodi are one of three species in the genus Paracheirodon (the other two being Paracheirodon erythromicron and Paracheirodon innesi). They can be differentiated from other members of their genus by four dark red stripes on their flanks and by having a black spot at the base of their tail fin.

The cardinal tetra does very well in aquariums as long as they have plenty of swimming space and if there is plenty of covers provided for them to hide in when they feel threatened or stressed out. If you have an aquarium with multiple cardinal tetras, then you will notice that each fish has its own personality, but most can be timid around large tank mates such as cichlids or aggressive tank mates like a betta.


Due to its warm water habitat requirements, and hence narrow temperature tolerance range of 24-28°C (75.2-82.4°F), Paracheirodon axelrodi is not recommended for home aquaria unless a heater is included in order to maintain stable water temperatures throughout all seasons. The aquarium should be planted densely with fine-leaved plants such as Cabombaceae, Cryptocoryne, and other difficult plants that grow well in medium light conditions.

These areas can be further decorated with pieces of bogwood, which allows breeding females to lay their eggs there. This species also tends to nibble on soft-leaved aquatic plants while they are young; therefore it is important to introduce them into an aquarium containing easily removed plant species such as Java ferns or Anubias nana, both of which will grow back if eaten by these fish.

Cardinal tetra size

The cardinal tetra fish can grow to about 3 cm (1.25 inches) in length.

Barbel Fish "Barbus Barbus"

Cardinal tetra tank size

The minimum recommended tank size for Paracheirodon axelrodi is 20 gallons

Tank set up

When you’re considering adding Paracheirodon axelrodi to your aquarium, it’s important to remember that they are a shoaling species. This means they need to be kept in groups of at least six individuals—more is always better. As such, any tank housing these fish should provide plenty of swimming room so they can move freely around each other and chase after their favorite food sources.

I keep my cardinal tetras in a 20-gallon tank with dim lighting and a sandy substrate. The bottom of the tank is covered with live plants (Java moss, Java fern, Hygrophila difformis ‘Ribbon’) and driftwood; overhanging branches above create little pockets for hiding spots.

Aside from those essentials, cardinal tetras require no specialized equipment or water parameters; if anything were to happen to them within an aquarium setting, it would usually have more to do with what has been introduced into their environment than anything else.

Cardinal tetra tank mates

The cardinal tetra is a schooling fish and must be kept in groups of five or more. These fish prefer an aquarium with neutral to slightly acidic water and soft to medium water flow. They should never be housed with overly aggressive cichlids or other aggressive species; they are also territorial and should not share an aquarium with other cardinal tetras.

They do best when they have plenty of live plants to swim around, both for aesthetic reasons as well as for shelter against aggression from tank mates.

Some good tank mates for your Paracheirodon axelrodi are danios, other tetras, such as rummynose tetra and serpae tetras, rainbowfish, small catfish such as Corydoras spp., nerite snails, and Indian Almond Leaves. Feed them a mix of high-quality flake food and freeze-dried or frozen live foods. The feedings should be spaced out so that they are eating only once every 24 hours.

Cardinal tetra breeding

Paracheirodon axelrodi

Since paracheirodon axelrodi is a popular aquarium fish with anglers, its breeding is well-documented. The cardinal tetra male builds a bubble nest. The male will guard and court females with his nest-building; if a female happens to visit his nest while he’s making it, she will deposit her eggs there. He will then fertilize them with milt and guard them until they hatch into fry (or become free-swimming) after several days.

Cichla Ocellaris "Butterfly Peacock Bass"

The fry initially lives off their yolk sac for about a week before starting to feed on zooplankton in the water column, which must be hand-fed for about another 10 days or so to get them eating reliably. This can be an amusing project for hobbyists looking for something new that isn’t too difficult or time-consuming but also yields considerable satisfaction from seeing them grow out of little dark spots in your tank into these vibrant little silverfish, darting around next to your glass walls.

Are Cardinal tetra aggressive or peaceful?

This freshwater species of tetra is usually peaceful and can be kept in groups of five or more. In some instances, Paracheirodon axelrodi can be aggressive towards other cardinal tetras and similar-looking species.

They live peacefully with other peaceful species of similar size, but small fishes are at risk from large adult cardinals taking advantage of their lack of ability to easily escape by making sudden dashes towards small prey fish. For example, swordtails and guppies may be eaten by adult cardinals if not given sufficient hiding places like tall plants

When keeping them in a community aquarium, it is important to research any possible tank mates beforehand.

Cardinal tetra care

Paracheirodon axelrodi

The cardinal tetra is a small freshwater fish that requires weekly water changes and lots of hiding places to feel safe. It’s more sensitive than other species in its genus (it’s a bit shy), so you have to be careful not to overfeed it. They enjoy live foods like brine shrimp or mosquito larvae but do not eat dead food very well. Some say a cardinal tetra tank should include some algae for optimum nutrition.

If your tank has a pH around 6-6.5, you may never need to add any supplements—that’s within range for normal algae growth. Don’t put your cardinal tetras into an established tank with unknown fish! You run the risk of introducing disease into your healthy population if they are exposed to toxins or chemicals from their new tank mates.

What do Cardinal tetras eat?

They are omnivores by nature, these tetras will eat all kinds of live foods including micro worms, bloodworms, and blackworms. They will also accept flake food and pellets. However, it is advisable to give them a varied diet for best results. Some hobbyists even feed them tropical sinking shrimp pellets and freeze-dried brine shrimp. These meats can be used as treats when training your paracheirodon axelrodi to take food from your fingers.

Vieja Synspilum (Redhead Cichlid)

Water parameters

Paracheirodon axelrodi

The ideal water condition should be a pH between 6.0 and 7.5, which is best for your tetras; the temperature should be set around 22 to 27 degrees Celsius (72-81 degrees Fahrenheit) and water hardness shouldn’t exceed 5 dGH. Keep nitrates as low as possible—10-20 ppm—and keep ammonia under 1 ppm or even better, 0 ppm. You should also aim for a carbonate hardness of 8 dKH.

Cardinal tetra lifespan

They can live up to 5 years in captivity.

Parasites and diseases

Unlike many other freshwater aquarium fishes, Paracheirodon axelrodi is hardy and disease resistant. It usually has no more than two diseases; a type of hole-in-the-head caused by infestation with worms (hole-in-the-head disease) and ich (white spot disease). While not fatal to Paracheirodon axelrodi if treated immediately, these diseases can cause significant damage to their gills and eyes respectively.


Axelrodi is a staple food for larger predators in its habitat. Native to South America, Paracheirodon is common prey for large predatory fish such as piranhas and characins. It is also eaten by aquatic birds such as jabiru (Jabiru mycteria), herons, and other large birds that do not swim in the water. Humans have been known to capture Paracheirodon axelrodi during fishing expeditions of lakes in South America.

Do Cardinal tetras make good pets?

Yes. Paracheirodon axelrodi are a beautiful species of freshwater tropical fish. These colorful and active little fish look great in an aquarium setting. If you are thinking about keeping these lovely little creatures as pets then you can’t be wrong.