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Cardinal Tetras: A Complete Care Guide (Diet, Tank & More)

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There is a variety of freshwater fish to choose from when setting up a home aquarium. A common species you will find in aquariums is the cardinal tetra! 

Read on to learn everything you need to know about caring for cardinal tetras, all the way from what they look like to where they originate from!

Cardinal Tetra Care Guide

Scientific Name:Paracheirodon axelrodi
Common Names:Cardinal Tetra, Red Neon Tetra, Scarlet Characin
Size:2 Inches
Minimum Tank Size:20 Gallons

Cardinal tetras are common in freshwater tanks due to their calm demeanor, small size, and bright colors. They are also easy to care for, and also fairly easy to breed. They are a great addition to any community tank.

Cardinal tetra in aquarium

Cardinal Tetra Appearance & Lifespan


Cardinal tetras are on the small end of the spectrum when it comes to freshwater aquarium fish. They are also quite popular amongst freshwater aquarium owners because they are docile and do well in a community tank. 

Cardinal tetras can typically grow up to two inches long. With that being said, the females are larger than the males. 

Colors and Markings

Despite Cardinal Tetras being small, they make up for their size with their beautiful coloring. They are vibrant red with iridescent blue stripes going from their head to their tail. You can’t miss them in a tank because they are so bright! 

A fun fact about cardinal tetras is that their colors are duller at night. However, if you notice that there is a dullness in their coloration during the day it could mean the fish has an illness that you should look into. 

On another note, two other types of cardinal tetras include the gold cardinal tetra and the albino cardinal tetra. The gold cardinal tetra is opalescent with a duller appearance than its counterparts. The albino cardinal tetra is translucent and is usually missing the iconic stripe but it can have a slight red stripe. 

Gender Differences

The cardinal tetra does not have that much of a difference between the males and females, which can make it a bit harder to differentiate between the two. The two biggest differences are that the females typically have a larger belly and are a bit rounder. This is more pronounced during mating season. 

The anal fin is also a differentiator between the two sexes. The male has a hook that protrudes from the anal fin, while the females do not. 


The lifespan of a cardinal tetra is dependent on its surroundings. For example, if they are well taken care of,  the cardinal tetra can live between 4 to 5 years in an aquarium. On the other hand, cardinal tetras only live around 1 year in the wild. 

Of course, if they are not taken care of with the correct water parameters and an unclean tank, the cardinal tetra may not live as long as they should.

Cardinal Tetra vs Neon Tetra

Neon tetras, as well as cardinal tetras, are two popular choices within the tetra family. They both can add beautiful colors to your tank. They are also both schooling fish and do best in groups of at least six; they thrive within larger groups as well.

Both the cardinal and the neon tetras also require similar tank setups and parameters since they live in similar environments in nature. Your tank should also include plants, as both tetras like having plant coverage to hide throughout the day and night.

Captivity Raised and Wild-Caught

Cardinal tetras are mostly wild-caught which makes them a bit harder to raise in an aquarium. They can be a bit more finicky with the tank parameters and are also hard to purchase in the first place. 

Since neon tetras are captivity raised, they are much more available than cardinals. They are also a bit easier to care for since they are already used to aquariums and they also tend to be cheaper to purchase than cardinal tetras.


Although they are similar in appearance and can look like they are the same, there are some differences.

The cardinal tetra is larger, and they have a red and blue stripe from head to tail. They have a more unique look that tends to be more visually appealing than that of a neon tetra. 

The neon tetra is also smaller than the cardinal tetra. They do not have the red and blue stripe down their entire body either. However, they do have blue and red colors, but for the neon tetra, the blue stripe runs down the entire body. 

The difference is that the red on the neon tetra is on the lower half of the body fading into a clear tail. Even though they are not as vibrant as a cardinal they are still beautiful. 

Diet & Feeding: Keeping Cardinal Tetras Healthy

Cardinal tetras are omnivores which means they eat both plants and animals. They should be on a diet containing a mix of pellets, vegetables (peas, cucumber, or broccoli), fish flakes, and live (or frozen) food, such as worms or larvae. 

Most of your cardinal tetras’ diet should also be high-quality flakes as they require a high-vitamin diet. This means that regular flakes found at a local chain store may not be sufficient, as opposed to high-quality food at a fish store.

It is also important to note that it is recommended to feed cardinal tetras about one to two times a day, only giving them an amount that they can eat within about three minutes. 

Suitable Tank Mates

Cardinal tetras are social schooling fish that do well with their kind or in a community tank with other similar species. If placed with other cardinal tetras, they should be in groups of about six or more. 

If there are not a group of tetras in the tank, the cardinal tetras you do have may hide most of the time out of fear. They can start to lose their color if they are always hiding as well. 

The following is a list of examples of suitable tank mates that are similar in size and have alike temperaments:

  • Neon Tetras
  • Pencil Fish
  • Corydora Catfish
  • Dwarf Gouramis

Undesirable Tank Mates 

Since cardinal tetras are small, it is also important to know which species of fish you should avoid mixing with your tetras to ensure they do not get hurt.

You should always avoid larger territorial fish that can easily eat the cardinal tetras. You should also avoid fish that are longer-finned, also known as fancy fish. This is because the cardinal tetras are known to nip fins and will go after those long fins on other fish. 

Examples of fish to avoid mixing your cardinal tetras are:

  • Angelfish
  • Cichlids
  • Gouramis
  • Bettas
  • Oscars

Ideal Tank Set-Up

A 20-gallon tank is ideal for a small group of six cardinal tetras. Increase the size of the tank by an extra two gallons per fish if adding more than 6. With that being said, an elongated tank is even better so there is more room for them to swim and explore. This makes the tank more spacious for the cardinal tetras to follow through with their schooling behavior. 

Having a dark sand substrate with roots and driftwood will make the tank similar to the river floor. Mimicking their natural habitat is key, so an isotope tank setup is what is recommended for cardinal tetras.  This not only is similar to their natural habitat but also really lets their colors shine. 

Ensure there is a secure lid for the tank as well. Surprisingly, cardinal tetras are known to jump out of the tank. This is mostly due to stress or if the tetras get scared. You should also ensure the filtration system you have has a slow or moderate current. This replicates what they are accustomed to in nature.  

Lighting is also crucial to the well-being of your cardinal tetras. You should have dim lighting since harsh light can be stressful for them. Adding live plants that can live in dim lighting is also a great idea. A few examples include java moss or cryptocoryne. 

Floating plants can also help keep the tank in dim lighting, as well as adding dried leaf litter to the top of the water.  This all helps create a blackwater environment that the cardinal tetra prefers. 

Aquarium Water Parameters

Since the cardinal tetra is mainly a wild-caught fish, it is very important to match the tank conditions with the blackwater creeks they originate from. They are moderately difficult to care for because they are more sensitive to parameters than other tetras. However, if the parameters stay in check they are easy to maintain.

It is also best to do partial water changes every week. This means changing about 25 % of the water at a time. This is because the cardinal tetra doesn’t tolerate poor water conditions.

It is also important to not add cardinal tetras to a newly cycled tank. Make sure a new tank is fully cycled prior to adding fish. Once the water parameters below are met, it is crucial to maintain those parameters so as to not stress or cause disease in your cardinal tetras. 

The below numbers are the basic water parameters that should be met:

  • Temperature: 73–81°F
  • pH Levels: 4.6-6.2
  • Water hardness: up to 4 dGH

Breeding Cardinal Tetras

Even though Cardinal tetras are harder to breed in a home aquarium, there are steps that need to be followed to make it a bit easier. If one pair does not breed, then try using a different pair while repeating the process until they do breed. Be patient, breeding Cardinal tetras are difficult, but not impossible!

  • Set up a breeding tank! A 5-gallon tank is a perfect size. There should be the dim lighting and shallow water. Water parameters for the 5-gallon breeding tank are:
    • Temperature: 75 F
    • Water hardness: 1-2 dGH
    • pH levels: between 5.5- 6.0
  • Prepare the pair for breeding by slowly raising water temperature a few degrees over the course of a few weeks. Feed them live food as well. You will want to add leaf litter into the tank to make sure the water is tannin-rich.
  • Place spawning mops and plants like Java moss (fine-leaved plants) in order to create a space for the female to lay eggs.
  • Put in an air-powered sponge filter to reduce current so it does not suck up the fry. 
  • Once the female’s stomach is bigger (this is when she is full of eggs) put the pair into the prepared breeding tank. Spawning typically happens in the evening over the course of several hours, the female produces an average of 130-500 eggs.
  • Once egg laying is finished, remove the parents so that they will not eat the eggs.
  • After one day, the eggs will hatch. They are free-swimming within four days. During this time, you can feed the fry liquid food or infusoria. After a few weeks, you can start feeding the fry baby brine shrimp.

Origin & Natural Habitat

The cardinal tetra originates from South America and is mostly found in the upper tributaries of the Negro and Orinoco rivers.  The Negro and Orinoco rivers go across the continent’s entire width, starting with Brazil in the east and going all the way west to Columbia. 

The cardinal’s natural habitat in these rivers consists of warm, black, and practically still waters. With the acidic pH in the water found in these rivers, the cardinal tetras live in water with practically no mineral content. 

As mentioned previously, the cardinal tetras do well in dim lighting. This is because, in their natural habitat, there is dense vegetation all throughout these rivers which means there is minimal sunlight.

As previously stated, cardinal tetras are schooling fish, they need to be in groups of at least six but more is preferred. This is because in their natural habitat, they move around in groups of hundreds, and they do everything as a unit. 

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