Cardinal Tetra: Species Overview

Category: Tetra

Common Names: Cardinal Tetra

Scientific Name: Paracheirodon axelrodi

Family: Characidae

Minimum Tank Size: 10 Gallons

Care Level: Medium

Temperament: Peaceful

Max Size: 2 Inches

Temperature: 72-80 F

pH: 5.5-7.0

Tank Level: Middle to Top

Colors: Blue, Red

Diet: Omnivore

Breeding: Difficult

Cardinal Tetra over Light Colored Gravel

Cardinal Tetra: Species Overview

The cardinal tetra shows captivating and colorful qualities. It lives peacefully in a freshwater tank or community aquarium. The scientific name is Paracheirodon Axelrodi, and they reach about two inches. These fish are active but easygoing and friendly.

Why are they so popular? This species is difficult to breed. However, it is popular for its beautiful bright red and neon blue color combination.

If you are creating your first home aquarium and never kept fish before, cardinals tetras make an excellent beginner fish suitable for various setups.

Distinguishing Features

Shimmering blue and red scales are the distinguishing features of the cardinal tetra. A radiant neon blue stripe runs from the nose to the tail with a vivid red stripe underneath and a soft white underbelly. Its soft fleshy fins are uniquely transparent with no color and fin nipping behavior.

There are a few varieties of the cardinal tetra species, including the betta fish, double tail, and half tail. The Crowntail is a variety of the betta, also called the Siamese Fighting fish. The double-tail betta has an exotic look with two distinct tails in various colors and designs.

Halftails, also known as half moon bettas, have elongated tails and flowing fins prone to tearing along and are more aggressive than other species.

Cardinal Tetras in Front of Plants


In their natural habitat, cardinal tetra originates from South America, far west as western Colombia. Specifically, this species primarily lives anywhere from the Orinoco River to the Rio Negro tributary of the Amazon River.

You can find them in fresh warm, clear, and soft acidic water in a slow-moving creek or stream that consists of silica sand. Although freshwater is best for tetras, they can live in brackish water. However, they won’t survive in pure saltwater.

Land plants or tall trees should be present to provide shade and maintain a steady water temperature. The aquatic plants tend to be yellowish that appear green in the sunlight.


Cardinal Tetras are known for a small body that typically reaches about two inches when fully grown. That makes this freshwater species ideal for compact tanks. Males and females look similar but differ in size. Males tend to be smaller than females (approx centimeters long).

The Typical Lifespan

The cardinal tetra species has a longer lifespan than most aquarium fish. The typical life expectancy is between 4 and 5 years when healthy. With the right environment, they can live longer than five years. A neon tetra could live up to eight years in the wild, but in an aquarium, that lifespan decreases to five years. In their natural habitat, the life expectancy shortens to about one year.

Cardinal tetras require stable conditions to live a long healthy life. Failure to maintain their needs could result in disease or premature death. While this species has a typical lifespan, the environment you place them in determines how long they will live.

Cardinal Tetra in Planted Tank Over Gravel

What can shorten the lifespan?

  • Sudden water changes
  • Exposure to direct sunlight.
  • Not starting with a clean well-cycled tank.
  • Not having the right water temperature,
  • No Proper Diet or right food for tropical fish.
  • Not Installing a good-quality filtration system.
  • Living with predators or aggressive fish in the same tank.
  • Not Mimicking Their Natural Habitat with plants, moss, rocks, etc.
  • Keeping your neon tetra in the bag too long before transitioning to a new tank.

Genders – The difference between males and females

Distinguishing the gender of cardinal tetra fish can be challenging if you are not a fish keeper. After some research, you will find differences between males and females. For example, males have different dorsal fins and colors. Female cardinal tetras have rounder, more prominent bellies compared to males. In addition, they are different colors with less distinct markings.

Here are some ways to determine the gender: 

Body Color – Male cardinals are typically brighter than females, known for a duller yellow color mixed with gray hues. However, if you are unsure about the colors, then it is best to look for other breeding behaviors of the fish.

Body Structure – Males are usually smaller and slimmer than females with a pointed dorsal fin. The females tend to have a round dorsal fin that is plump and broad. In addition, males flare their fins during courtship, whereas females do not.

Breeding Behaviors – One must watch the breeding behaviors to determine the gender. For example, males are very active and aggressive when reproducing and court the female by swimming around her. The females are less active and stay near the tank’s bottom.

Aggression – Male cardinal tetras, are more aggressive than females, especially in breeding mode. So, if there are any other fish in the tank, it is best to keep them separate during this time to avoid being a target.

Nesting Behaviors – Most freshwater fish reproduce by building nests and laying eggs. Males often build their nests out of plants and other materials, then aggressively guard their territory and the eggs inside. The females will lay their eggs in the male’s nest.

Two Swimming Cardinal Tetras

The Temperament

The temperament of cardinal tetras is very peaceful, playful, and mild. However, they are also very energetic and active social schooling fish during the day. You won’t find these fish engaging in roughhousing or bullying. Aggression is rare unless during feeding or breeding.

In a small group, they may act more anxious, but in a large group setting, they are more confident and often protective of each other. Cardinal Tetras also get along with other small fish and may follow or swim alongside their tank mates.

These fish are in constant motion darting around the top of the tank. They enjoy exploring caves or hiding under leaves and logs. Their demeanor makes them suitable for aquariums and first-time fish owners.

Male vs. Female Temperaments

Males are not aggressive but can be territorial with other cardinal tetras. Therefore, having only one male in the aquarium is best because two would fight until one dies (or both).

The males and females rarely fight with each other. However, when they do, it is over territory or food. You can keep them together in the same tank if there are ample places to hide.

Tank Parameters

The minimum tank size for cardinal tetras is 10 gallons (57 l). While this can be acceptable for a very small group of young cardinals, a larger tank will help to keep your fish happier and healthier.

Cardinal tetras do best when in warm water that is 72 to 80° F. They can survive a few degrees cooler than these for a time. They cannot withstand heat of greater than 81 degrees, however. The water aciditity range should be neutral or slightly acidic between 5.5 to 7.5 pH., and some slight difference is acceptable

Two Cardinal Tetras on White Background

Tank Setup


Fine sand or substrate that resembles riverbeds and acts as the perfect anchor for plants (if applicable). While substrate isn’t technically required, it has many positive impacts on your tank.

First it provides additional surfaces for beneficial bacteria to grow which contributes to healthy water parameters. Second, it provides anchors for decorations. And finally, it improves the look at the tank. Not only does it just look nice, it also helps to “hide” fish waste by camouflaging it.


You can select any type of fish safe decorations. Fish always like having options for places to hide so consider that when selecting and placing decoration. Cardinal tetras also need open space to swim so don’t overdo it.


While live plants are preferred, fake plants are perfectly acceptable. Live floating plants and submerged plants like Anubias, Java Fern, and Amazon Swords are great options as they look great and are easy to maintain.


Low to moderate adjustable lighting that is 4500K if you have live plants. With artificial plants, you have nearly unending options with lighting. Just be sure to select something water safe that won’t overheat the water.


A filtrations system is required for all but the most advanced fishkeepers. Use an internal filtration system, hang-on-back, or an under-gravel filter.

Cardinal Tetra Swimming in Front of Leafs


Cardinal tetras are omnivores. They are flexible and eat most of the foods in their tank at meal times. Therefore, you should create a well-balanced diet. Food can range from freeze-dried, frozen and even live food if they get hungry enough.

They prefer meaty foods. A good rule of thumb is to incorporate food containing protein, fibers, and omega-fatty acids. Depending on the size, the food may need to be broken into smaller pieces for digestion. Some recommended foods for community aquariums:

  • Brine shrimp
  • Tubifex
  • Insects
  • Daphnia
  • Larvae
  • Bloodworms
  • Fruit flies
  • Ubifex
  • Veggies (spirulina, lettuce, chopped algae, spinach, cucumber, etc.)
  • Flake and pellet food

How Much Should I Feed Cardinal Tetras?

Aquarists must feed cardinal tetras fish at least twice a day, in the morning and at night, if possible. Meal amounts should be what they can eat under three minutes. If there is still food left after three minutes, remove the extra food with a fishnet. If their stomachs bulge, end the feeding to prevent overeating.

The Breeding Process

The cardinal tetra is popular aquarium fish, but it is challenging to breed because it isn’t an easy process. Perhaps this happens because of the spawning process, which takes place in soft water. If not, the eggs will not fertilize.

It will require you to provide special conditions that mimic their native environment in South America. This species will not produce babies if they do not feel comfortable in their surroundings, and they must be at least a year old to breed.

A week before the breeding cardinal tetra male and female, the pair is plentifully seated and fed. Next, there is a transfer to the spawning area, where the male begins courting the female, which lasts up to 7 days, after which spawning happens in the dark.

A separate breeding tank is helpful, and it must have steady water chemistry with a pH of 5.0 to 6.0 and soft water of 3 to 5 dGH or below. The female typically lays between 130 and 500 eggs that fall to the ground.

The best temperatures for breeding range from 77-82 degrees Fahrenheit. Therefore, one must use an aquarium heater if the Cardinal tetras are not living in this temperature range already.

These fish release their eggs in the water instead of attached to plants or other objects. Producers should be moved out of the aquarium so that they do not eat their caviar. This species eventually reaches a mature size of up to two inches in the aquarium.

It is better not to breed a cardinal tetra in an aquarium, so you should create a separate spawning tank with a volume of about 15-20 liters with the best water quality. A 50% water change the day before you bring home any new cardinal tetra is always a good idea.

Cardinal Tetra in Planted Tank Over Gravel

Common Diseases

The cardinal tetra is usually healthy and can thrive as long as they are in the right living conditions. However, they are also vulnerable to many chronic diseases due to their environment and tank mates.

Keeping a tank with proper water parameters, enough space, and a well-balanced diet can prevent these diseases. In extreme cases, one should consult with a fish veterinarian.

One of the first signs a fishkeeper will notice is that the affected fish no longer interact with the other fish.

Other symptoms include restlessness, loss of color, cysts, swimming changes, and lumpy appearance. Eventually, swimming becomes more erratic before the fish appears ill.

What are the most common diseases?

  • Swim bladder disease
  • Ich
  • Fin rot
  • Velvet
  • Mouth warts
  • Bacterial infections
  • Black spot disease

Secondary infections could appear from neon tetra disease. Fish with this disease must be placed in quarantine as soon as possible to stop any spreading. There is no cure for neon tetra disease, and therefore the euthanization of the fish is usually the only option.

Lots of Cardinal Tetras in Heavily Planted Tank

Potential Tank Mates

One of the main rules of the aquarium is to determine the potential tank mates.

The cardinal tetra thrives with others of its kind in groups of 6 or more.

It is recommended to select tank mates carefully and stick with species that are less than 2 inches in length. They are often ideal in group tanks with small species that are docile. The best types of fish to pair with cardinal tetras include:

  • Neon tetras
  • Pencil fish
  • Rasboras
  • Dwarf gouramis
  • Hatchet fish
  • Corydoras catfish
  • Barbs
  • Freshwater shrimps, crabs, and snails

Cardinal tetras are sensitive fish, so living with toxic tank mates can cause stress and aggression. They should not be paired with large or predatory fish that could potentially eat them. Tank mates to avoid are bettas, cichlids, angelfish, long-finned fancy fish, and larger gouramies because cardinal tetras like to nip long fins.