Cardinal Tetra – A Complete Care Guide

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Cardinal Tetra is a popular freshwater fish adored by fish-keepers for its easygoing nature. They are colorful, tropical fish that are often misunderstood as Neon Tetra and Green Neon Tetra. The scientific name of Cardinal Tetra is Paracheirodon Axelrodi, which is a tribute to one of the greatest fish experts of all times—Herbert R. Axelrod.

There’s much more to explore about this beautiful fish that will take you by surprise. Therefore, stick with me for a beautiful fish experience.

Species Overview

Scientific NameParacheirodon axelrodi
Common NamesCardinal Tetra, large neon tetra, red neon, roter neon.
OriginAmazon rivers, particularly, Brazil, Colombia, and Venezuela
Care LevelIntermediate
Lifespan4 to 5 years
Tank LevelTop to mid-dweller
Minimum Tank Size20 gallons
Temperature Range73 to 81 degrees F (23 to 27 degrees C)
Water HardnessUp to 4 dGH
pH Range4.6 to 6.2
Filtration/Water FlowLow to moderate
Water TypeFreshwater
BreedingEgg layer
Difficulty to BreedIntermediate
CompatibilityCommunity tanks
OK, for Planted Tanks?Yes

What is a Cardinal Tetra?

Cardinal tetra is one of the most popular freshwater fish that is excellent for community tanks. They are highly active, social fish with a peaceful nature. They are small fish with slim, slender bodies ideal for a small tank.

Though easy to care for, these species are not easy to breed in captivity. Therefore the chances of breeding cardinal tetras successfully are very thin.

Origin and Habitat

In their natural habitat, cardinal tetra comes from South America, especially the Amazon river. Needless to say, these schooling fish are tropical fish that prefer warm water temperature and soft acidic water. They mostly inhabit the slow-moving waters in Venezuela, Brazil, and Colombia.


The Cardinal tetra is a beautiful, vibrant, colorful fish with a reddish brown coloration extending from the mouth, eyes, and tails, covering most of the lower body. Right above this reddish brown line lies a greenish-blue stripe that divides the body. The dorsal and anal fin of Cardinal tetra possess no color, and the body showcases red stripes, longer than the red neon tetra. These longer red stripes are the distinguishing factor between the Cardinal tetra and red neon tetras.

Cardinal Tetra Fish

From the mouth and eye to the tail runs a reddish-brown coloration covering most of the lower body. Above that runs a green fluorescent band. The dorsal and anal fins have no color. The male is less thick in the body than the female. This species is not easy to breed. Suitable pairs are picked by observation and kept apart feeding with live food to get them ready.

There is a small, silver area along the ventral surface of the Cardinal tetra with the lower body; bright red. In fact, the name, Cardinal Tetra is derived from this bright red color that resembles the red robes of the Cardinals.

Average Size

The Cardinal tetra is a small freshwater aquarium fish that grows up to 2 inches in length. They occupy the middle level of the tank mostly, thus, remain happy with other fish that are bottom or surface-dwelling.


In their natural habitat, the life expectancy of a Cardinal tetra is very short, i.e., about a year. However, in captivity, they are known to live for around five years or longer, if their requirements are met.


Cardinal tetras are hardy and very easy to care for beginners. However, bear in mind that minor negligence can cause potential damage to your beloved finned friends.

Therefore, it’s recommended to follow this care guide to raise healthy and happy Cardinal tetra in an aquarium.

Here’s a summary of what needs to be followed to care for your Cardinal tetra.

  1. Keep them with other fish that are similar or smaller in size to avoid stress and other illnesses.
  2. Always aim to provide slightly acidic and very soft water in your aquarium tank.
  3. Keep the aquarium clean and hygienic and feed them more live foods than commercial food.
  4. Fill your tank with big-leafed plants to help them scatter their eggs while breeding.

Aquarium Setup

The Cardinal tetra is a small tropical fish that need ample room to swim despite its small size. Also, they don’t appreciate cramped living conditions in a tank. Thus, I recommend setting up a tank that is longer rather than taller, such as the wall-mounted aquarium lines.

Cardinal Tetra

Also, they are middle dwellers, peaceful, schooling fish. Thus, I suggest keeping them with companions that are bottom-dwelling or surface dwelling.

Tank Size

As mentioned above, despite their small size, Cardinal tetras love free swimming space. Therefore, I suggest a tank size of no less than 10 gallons to accommodate only one or two of them. However, if you’re getting a shoal of Cardinal tetra species or other tetra species with a group of six or more which is recommended, it’s crucial to go for a tank size as big as 20 gallons.

Water Parameters

In the wild, the water is soft and slightly acidic. And to keep cardinal tetras happy, you should also aim for acidic water.

The ideal pH range for Cardinal tetra is around 4.6 to 6.2. The cardinal tetra is known to tolerate a pH level of up to 7.4. However, it is recommended to keep it below 6.

The ideal water temperature for your Cardinal tetra tank is around 73°F to 81°F, thus, replicating the water parameters of their natural environment. Besides, the carbonate and bicarbonate levels in your aquarium tank should be around 2 to 6 KH. Also, the water hardness should exceed 4 dGH.

Filtration and Aeration

Sure, cardinal tetras are small freshwater fish, but they are vulnerable to the toxic elements in the water. For example, nitrates and nitrites. Therefore, setting up a good filtration system is crucial.

Since cardinal tetras are schooling fish, experts advise keeping them in groups. However, many novice aquarists when keeping them in groups underestimate the power of a filter. As a result, uneaten food, fecal matter, and other debris accumulate in the tank and release harmful toxins such as Ammonia. Thus, installing a high-quality filter that adds oxygen and a little movement in the water is highly recommended.

Nonetheless, some aquarists skip the filter and add many live plants in the aquarium that consume Ammonia and keep the tank oxygenated and less polluted. However, if you’re a complete novice, I don’t suggest skipping the filter as it will lower the maintenance of your tank and keep your fish healthy and happy for long periods. Also, you won’t have to change the water regularly.

Best Aquarium Filter for this type of Fish

You can install canister filters. However, they are not within the budget of some hobbyists. A more budget-friendly option would be to purchase a hang-on back filter like a Hagen Aquaclear. You might want to consider putting on a sponge on the intake of the filter so as to not have these tiny fish sucked up by it.

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In their natural habitat, the cardinal tetras come from warm, slow-moving water with densely vegetated areas. Therefore, the sunlight is usually filtered by plants.

Thus, I recommend setting up your aquarium lighting to low or moderate levels and adding lots of floating or rooted plants to filter the light.

Aquatic Plants and Decorations

If you plan on breeding cardinal tetra, I cannot emphasize the importance of aquatic plants enough. Plants provide your Cardinal tetras with a hiding space with an open swimming space. I suggest keeping floating plants in the aquarium that provides hiding places for your cardinal tetras.


Cardinal tetras are at their best in an environment that mimics their habitat. Thus, going for a muddy substrate or sandy is your perfect bet. If you have a planted tank, you should consider a planted tank substrate in order to support the growth of your plants.

Community Tank Mates

Cardinal tetra is a shoaling fish that lives in shallow rivers and prefers to live in a group of at least 6 fish in a 20-gallon tank. However, if you have more room, cardinal tetras would warmly welcome their tank mates. The ideal tank mates for cardinal tetras are:

  1. Neon tetra
  2. Green neon tetras
  3. Ember tetras
  4. Black skirt
  5. Emperor tetras
  6. Zebra Danios
  7. Chili Rasbora
  8. Dwarf Gouramis
  9. Guppies
  10. Hatchetfish
  11. Mollies
  12. Angelfish
  13. Small catfish
  14. Otocinclus
  15. Loaches
  16. Dwarf shrimps
  17. Snails

I suggest avoiding any aggressive and large fish (Goldfish, aggressive cichlids, etc) that would lead to unnecessary stress to your cardinal tetras.


Well, breeding cardinal tetras can be a daunting task. You need to follow the water chemistry of Amazon and its subsidiary rivers as close as possible to attain successful breeding. Here is a video below for those who want a visual reference.

For example, the tank water should have low mineral content with slightly acidic water, clean, and soft. The water temperature should be around 73°F to 81°F. Even though cardinal tetras are easy to care for and somewhat low maintenance, however, when it comes to breeding, the situation changes completely. 

In the wild, the water is loaded with natural vegetation that forms a shield for direct sunlight. Thus, in such an environment, cardinal tetras spawn in large numbers. They lay eggs in large numbers. When the eggs hatch, the new fish is protected by nature and have enough food and places to hide.

However, in captivity, the breeding process depends on many factors, such as water hardness and other water parameters. When the requirements are not met, the adult cardinal tetras face difficulty in spawning and hence breeding.

Requirements for a Separate breeding tank

Even if you provide cardinal tetras with the ideal water conditions, they have a habit of eating their own eggs. Thus, to avoid all these problems and overcome the difficulties in the breeding process of cardinal tetras, here are some suggestions.

  1. Set up a separate breeding tank when the male tetras and female tetras are ready for spawning
  2. In the breeding tank, place the female cardinal tetras in the morning and male tetras in the evening
  3. Keep the water parameters optimal and the tank clean. Filter the tank regularly and remove debris, uneaten food, and other particles.
  4. Feed cardinal tetras nutritious food to boost their immunity. Increase the proportion of live foods such as brine shrimp and small crustaceans.
  5. Maintain the water temperature slightly higher than the normal temperature. 
  6. Monitor the eggs carefully after spawning. The eggs of cardinal tetras are extremely photosensitive. Therefore, keep them in the dark
  7. Remove the adult cardinal tetras from the tank right after the eggs are laid to protect the eggs from their own parents
  8. The fry usually comes out within 24 hours. Keep your tank dimly lit as they are sensitive to light for the first week
  9. Feed cardinal tetras fry liquid food. After 2 to 3 days, start feeding them baby brine shrimp and sifted Daphnia
  10. The fry of cardinal tetras grow slowly and become adults after 10 weeks
  11. Keep the temperature within the recommended range and the tank clean. The color of cardinal tetras fades away if the water conditions are not favorable

The breeding process becomes easy as a breeze if you take care of the water conditions and hygiene of the tank.

Food and Diet

The best thing about raising cardinal tetras is effortless feeding. They are omnivores and opportunistic feeders that even eat plant matter. Thus, you can feed them anything. Dried or flakes food, live and frozen foods with meaty snacks. I don’t recommend feeding them live food regularly as they will refuse flaked or dry food, which is not acceptable. Dry food is loaded with vitamins and is much cheaper and more accessible than live or frozen food. Also, you can avoid many diseases that come with infected live foods.

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Thus, I suggest keeping their base diet around 75% on dry food and occasional live or frozen foods as treats. Some meaty treats include Bloodworms, brine shrimp, fly larvae, insect eggs, as well as water fleas like Moinia and Daphnia.

How often should I feed them?

You should feed your tetras at least twice a day with enough food that they can consume in around 2 minutes. The food that remains in the water after 3 minutes should be instantly removed to maintain tank conditions and avoid fish overfeeding.

Common Health Problems and Diseases

Like other fish, cardinal tetras are also susceptible to certain fish diseases and infections. They can also get neon tetra disease.


The Neon tetra disease is caused by harmful parasites that spread like a wildfire and are fatal to the fish. When the fish suffers from neon tetra diseases, it is recommended to remove it as soon as possible from the tank and quarantine it as this disease is highly contagious.

Gill Flukes

This disease is also caused by the parasites in which the gills of cardinal tetras serve as a host for fluke and provide it with the nutrition to grow and multiply in big numbers. The common symptoms of gill flukes are:

  1. Rubbing the body on the bottom or sides of the tank
  2. Rapid, abnormal gill movement
  3. Lethargy

Fin Rot

Fin rot disease is caused by harmful toxins such as nitrates, which leads to the loss of tissue from fins, tail, or even the body of cardinal tetras. Therefore, strive to maintain the water conditions of your tank with a proper filtration system and weekly or biweekly water changes. The symptoms of fin rot include:

  1. Damaged gills
  2. Ulcers on the body
  3. Loss of color
  4. Loss of appetite

Differences Between Male and Female

They both grow around 2 inches in length. However, the females are rounder than their male counterparts. Also, the male tetras have a small hook present on their anal fins while females lack it.

Where To Buy

You can purchase Cardinal Tetras at most local fish stores. You can also purchase them through online retailers, where they will happily ship your fish overnight. If you are going to try an online shop, I highly suggest trying Flip Aquatics. Rob and his team do a fantastic job taking care of their livestock. You can use promo code ASDFLIPPROMO for a discount!


Are they aggressive?

No, cardinal tetras are small peaceful tetras, schooling fish that can easily live in community aquariums.

Which is better cardinal or Neon Tetra?

Both the tetras have their own distinctive properties. If you’re low on budget and have a smaller tank, then go for Neon Tetras. However, if budget is not a problem and you want vibrant addition to your aquariums, then cardinal tetras are your go-to option.

What is the difference between Neon Tetra and cardinal tetra?

When it comes to appearance, neon tetra and cardinal tetra are almost identical. However, cardinal tetras are one inch longer than Neon tetras.

Also, neon tetras are easier to care for than cardinal tetras with a less demanding nature and for breeding purposes, neon tetra doesn’t pose any challenge. However, cardinal tetras are difficult to breed in captivity. Either way, they both are an excellent addition to home aquariums.

Are they a freshwater fish?

Yes, Cardinal tetras are freshwater fish that comes from South America, originating from the Orinoco River to the Rio Negro tributary of the Amazon River.

Are cardinal and neon tetras the same?

No, Cardinal tetras and Neon tetras are two different species from the same family. However, they look similar and are often misunderstood by novice fish keepers. Cardinal tetras have strips that go across their entire bodies while neon tetras’ red stripes only go halfway.

How big of a tank do thry need?

Despite their small size, these fish need ample swimming space to thrive in an aquarium. Thus, a tank of around 10 gallons is a bare minimum for one or two species. But if you’re keeping a group of six or more, I recommend getting a 20 gallons tank or more. 

Are they Hardy?

Moderately, yes. Cardinal tetras are easy to care for as long as their water requirements are met. However, as compared to neon tetras, they are pretty high maintenance. 

Final Thoughts

Cardinal tetras are exquisite freshwater aquarium fish that add vibrancy and elegance to your home aquarium. However, difficult to breed, they are pretty easy to care for and opportunistic feeders that feed on almost everything.

I recommend quarantining your fish before adding them into your home aquariums since they are usually being sold in the aquarium trade as wild-caught fish. This would prevent the spread of diseases and illnesses.

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