Cardinal tetra Care Guide: Diet, Tank Mates, Diseases, Breeding & More

Updated: December 17, 2022

The cardinal tetra is a beautiful freshwater fish that is perfect for beginner aquarium owners. They are relatively easy to care for and are very peaceful, making them a great addition to any community tank.

This guide will teach you everything you need to know about cardinal tetra care. You’ll learn about their diet, size, lifespan, and more!

Species overview

The cardinal tetra (Paracheirodon axelrodi) is a freshwater fish that’s native to the Orinoco River basin in South America.

They are a very popular choice for aquariums because of their bright red coloration. Cardinal tetras are also very peaceful fish and can be kept with a wide variety of other species.

In the wild, cardinal tetras eat a diet of small insects and crustaceans. In captivity, they can be fed a diet of small live or frozen foods.

Cardinal tetras are very sensitive to changes in water quality and should only be kept in aquariums that are well-maintained.


Cardinal tetra

The first thing you’ll notice about this fish is their bright coloration. Cardinal tetras are a beautiful blue on their backs that fades into a bright white on their bellies.

This coloration is very striking, especially when you see a school of them swimming together. The blue on their backs is actually iridescent and can change shades depending on the angle that you’re looking at them.

You’ll also notice a black stripe that runs along their lateral line. This stripe is almost horizontal and goes from their gills to the base of their tail fin.

The fins on a Cardinal tetra are all clear and very thin. The dorsal fin is slightly taller than their anal fin and both of these fins are shorter than their caudal fin.

Their bodies are long and thin, giving them a hydrodynamic shape that helps them swim quickly.

Cardinal tetras are a small fish, only growing to be about 2.5 inches (6.4 cm) in length.


In the wild, cardinal tetras have a lifespan of around 5 years. In captivity, however, they can live up to 10 years with proper care.

The main thing that will determine how long your cardinal tetra lives is the quality of the water they’re kept in. These fish are very sensitive to water conditions and will not do well in an unhealthy environment.

As long as you keep a close eye on your tank’s water quality and make sure the parameters are within the ideal range, your cardinal tetra should have no problem reaching their full lifespan.


Cardinal tetras are relatively small fish, only reaching an average length of 2.5 inches (6.4 cm) when fully grown.


Tank Size

The minimum recommended tank size for a school of cardinal tetras is 30 gallons.

While you can technically keep a school of cardinal tetras in a smaller tank, we don’t recommend it.

A smaller tank means less water volume to dilute waste and chemicals, which can lead to a more toxic environment for your fish.

It also means less space for your fish to swim and explore, which can lead to boredom and stress.

If you’re set on keeping cardinal tetras, we recommend a tank size of at least 30 gallons.

Water Parameters

The cardinal tetra is a freshwater fish that is native to the Orinoco Basin in South America.

They are found in slow moving waters that are heavily vegetated. This provides plenty of places to hide and forage for food.

The water parameters you need to maintain for cardinal tetras are:

  • Water temperature: 72 to 82 degrees Fahrenheit
  • pH levels: 6.0 to 7.8
  • Water hardness: 2 to 12 dGH
  • Alkalinity Levels: 4-8 dKH

What To Put In Their Tank

Cardinal tetras are a schooling species, which means they’re going to feel more comfortable when they’re in a group.

The minimum group size we recommend is 6, but if you can manage more then that’s even better.

Cardinal tetras are a relatively small species, which gives you a lot of flexibility when it comes to the size of their tank.

We recommend a 30-gallon tank as a minimum, but you could probably get away with a 20-gallon if you needed to.

When it comes to setting up the inside of their tank you have a lot of options.

We recommend going with a dark substrate since it will help bring out their colors. You can also include some plants (real or fake) and driftwood if you’d like.

Just avoid anything that’s too big or bulky since it will make the inside of the tank feel cramped.

Common Diseases

The Cardinal tetra is a very hardy fish, which means that it doesn’t often fall ill. However, that doesn’t mean that it’s immune to disease.

There are a few illnesses that these fish are prone to, the most common being ich. This is a parasites that affects freshwater fish and can be quite serious if left untreated.

The most obvious sign of ich is the presence of white spots on the body of your fish. If you notice this, it’s important to act fast and begin treatment immediately.

Other potential diseases include Swim Bladder Disease, Hexamita, and Columnaris. While these are less common, they can still be a problem if your fish are kept in subpar conditions.

As with any other fish, the best way to keep your Cardinal tetras healthy is to provide them with a clean and stable environment. This includes clean water, a good diet, and plenty of hiding places.

If you can do that, you’ll greatly reduce the chance of your fish getting sick.

Behavior & Temperament

Cardinal tetras are schooling fish, which means they do best when they’re in groups. In the wild, they can be found in shoals of hundreds of fish. So, it’s no surprise that they feel more comfortable when they’re around others.

These fish are relatively peaceful and get along well with other fish that have a similar temperament. They’re not known to be aggressive, but they may nip at the fins of other fish if they feel threatened.

Cardinal tetras are active fish that enjoy swimming around. They’re constantly in motion, which is why they do best in tanks that are at least 10 gallons. They need the space to move around and explore.

Tank Mates

Cardinal tetras are native to the clear waters of the Amazon basin. As a result, they’re not too particular about water conditions.

The main thing to remember is to avoid adding fish that are too large. Cardinal tetras are small and delicate, so tank mates that are too big might see them as a snack.

Other than that, there are tons of cardinal tetra tank mates to choose from. These fish are compatible with most species, including:


Cardinal tetras are one of the most popular fish in the aquarium trade. They’re gorgeous fish that add a splash of color to any tank. And, they’re not too difficult to breed in captivity.

To start, you’ll need to set up a breeding tank. It should be at least 20 gallons and hold 2-3 gallons of water per cardinal tetra. The tank should be well-filtered and have a good amount of plants.

Cardinal tetras prefer soft water, so you may need to add a water conditioner to the tank. The pH should be between 6.0 and 7.0. The temperature should be between 75 and 80 degrees Fahrenheit.

When the tank is ready, add 3-4 females for every male. The males are smaller than the females and have longer fins.

Feed the fish live foods and quality flakes. After a few weeks, you should start to see the females getting rounder. That’s a sign that they’re full of eggs.

When you see this, it’s time to set up your spawning mop. This is just a piece of yarn or string that the female can lay her eggs on. Make sure that the mop is anchored down so it doesn’t float away.

You may see the female chasing the male around the tank. This is normal behavior. The female is just trying to get the male to release his sperm on the mop.

Once the eggs have been laid, remove the parents from the tank. The eggs will hatch in about 24 hours.

The fry are very small and need live foods to survive. You can feed them baby brine shrimp or other small organisms.

As they grow, you can slowly transition them to flakes or pellets.


Cardinal tetras are a beautiful fish that are perfect for beginner fish keepers. They are easy to care for and are very peaceful, making them a great addition to any community tank.

With their striking red coloration, they are sure to add some flair to your tank. Cardinal tetras are also relatively hardy fish, so they are a great option for those just starting out in the fish keeping hobby.

Overall, we think cardinal tetras are a great fish for beginner and experienced fish keepers alike.