Cardinal Tetra Expert Care & Tank Set Up Guide For Beginners

Cardinal Tetras would be a truly exquisite addition to any tank with their stunning red and blue bodies.

A wonderful addition to a community tank, the sight of sparking schooling cardinals is a joy to behold.

This straight-to-the-point Cardinal Tetra expert care guide will provide you with all the knowledge needed for the proper care for a flourishing school of cardinals.

Origins & Appearance of Cardinal Tetras

The Cardinal Tetra is a tropical freshwater fish that is one of the most known and loved small tetras. Similar to the Neon Tetra, it comes from the Paracheirodon genus of the Characidae family and is scientifically known as P. axelrodi.

It has a petite body that typically reaches a size of 1.5-2 inches. Its shimmering blue and red scales are mesmerizing to behold, where they seem to glitter and shift in color from sapphire blue to turquoise when viewed from different angles. 

Close up of cardinal tetra (Paracheirodon axelrodi) in freshwater aquarium

Hailing from South America, the Cardinal Tetras are commonly found in the upper tributaries of the Orinoco and Negro rivers. These rivers extend all across the continent’s width from Brazil in the east, passing through Venezuela to Columbia in the west.

They come from warm, clear, slow-moving/still waters. These waters usually have an acidic pH with almost no mineral content. The fish have very dim lighting as any sunlight is filtered by the surrounding dense vegetation.

Cardinals Tetras usually move in shoals/schools of hundreds, swimming and feeding as one unit in shallow rivers and streams. Such group behavior serves as a defense mechanism against larger predators, as they’re less likely to be picked off when traveling together.

Most aquarium-raised Cardinal Tetras come from the wild, where they can be found in abundance. Nowadays, tank-bred varieties are also found, although not as much, as they can be very hard to breed.

Care Stats Overview

  • Common Name: Cardinal Tetra, Large Neon Tetra, Red Neon, Roter Neon
  • Tank size: 20 gallon
  • Temperature: 73-81 °F (23-27 °C)
  • pH: 4.6-6.2
  • KH: 2-6 kH
  • Living zone: Top to mid-dweller
  • Temperament: Peaceful
  • Size: 2 inches
  • Diet: Omnivore

Scientific Classifications

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Characiformes
  • Family: Characidae
  • Genus: Paracheirodon
  • Species: P. axelrodi

Life Span

Cardinal Tetras live around five years on average when raised in an aquarium. Some lucky fish can even reach ten years of age when properly taken care of.

They have much shorter life spans in the wild, only living to about a year or so. Conversely, the Neon Tetra has a shorter life in captivity than in the wilderness.

Cardinal Tetra Sexual Dimorphism: Colors & Markings

Cardinal Tetras have truly mesmerizing colors, similar to Neon Tetras, but specific features set them apart from each other.

Both Cardinal and Neon Tetras have a metallic blue stripe extending across their body, from nose to tail. However, the red stripe underneath the blue one differs between the two species.

In the Cardinal Tetras, the red stripe also extends throughout the length of the fish, while that of a Neon Tetra only covers from mid-body to tail. That is why Cardinal Tetras are also called the Red Neon Tetras.

Their red stripe gradually fades into a clear tail. They have a white underbelly and transparent fins, similar to their tail. Some varieties of Cardinal Tetras are gold or silver-blonde in color, but they’re very hard to find.

Cardinal Tetras usually grow up to about 2 inches, with the females being slightly more bulbous and rounder than their mates. The size difference is more obvious to the eye during the mating season but can be quite hard to notice at other times.

Fortunately, one more feature that can help you differentiate between males and females is available. Look for a small hook present on the anal fin. If you can see it, then you’ve found your male tetras.

Cardinal Tetra Care & Tank Set-Up

Schooling cardinal tetra (Paracheirodon axelrodi)

Tank Size & How Many Can Be Kept Together

Cardinal Tetras can be kept in a 10-gallon tank if there are only one or two of them. However, it’s generally recommended to keep them in at least a group of six.

They swim in large groups when in their natural habitat; therefore, it’s essential to provide them with some company to make them feel brave, confident, and stress-free.

So, to accommodate a group of six or preferably more, a 20-gallon tank is much more appropriate than a 10-gallon one. Make sure to provide 2 gallons of extra space with every new addition so that your fish can swim to their hearts’ desire without feeling limited or constrained.

The Nitrogen Cycle

Any aquarist/hobbyist will have heard about the nitrogen cycle. It’s present in every single tank and should be closely monitored for the health and longevity of all fish and aquatic creatures.

If you’re unfamiliar with the concept, it’s basically the gradual breakdown of toxic substances -like ammonia and other nitrogenous substances- into less harmful products. These remaining products can then be easily eliminated from the water by plants or other means.

Like any other fish, Cardinal Tetras need a stable, fully cycled tank with regular water changes to ensure that the toxin levels are in order and pose no harm to the tank inhabitants. Change about a quarter of your water every week and monitor the water in-between the changes using test kits.

If you’d like to know more about the nitrogen cycle and how to cycle your aquarium adequately, take a look at this article.

Water Parameters

  • Temperature: Your tank’s water is to be kept at a temperature ranging from 73°F to 81°F (23 to 27°C). This is to replicate the same warm climate from which Cardinal Tetras come.
  • pH: The pH has to stay slightly acidic to match that of its natural habitat, so stay around the 4.6 to 6.2 range. It can tolerate up to a pH of 7.5, but it’s preferable to remain below 6. If you’d like to know how to lower your tank’s pH, click here.
  • KH: The carbonate and bicarbonate levels should be roughly about 2-6 KH.
  • Hardness: Cardinal Tetras live in incredibly soft waters with very low mineral concentrations. So your water’s general hardness shouldn’t exceed 4 dGH.

Tank Set-Up

Once you’ve established your water’s parameters, you should start setting up your tank to suit your tetra’s preferences and ensure their comfort and well-being.

To achieve this, you should set up your tank to be as similar as possible to the tetra’s natural environment. The first step is to add a substrate that mimics the river floor, namely sand or mud. These substrates will serve as the perfect growing ground for live plants.

Next, set up your lighting to low-moderate levels and make sure to add floating or rooted plants to filter the light reaching the fish. Another benefit provided by the plants is acting as hiding spaces for the tetras when feeling stressed, threatened, or sick. Amazon Sword, Java Fern, and Anubias Nana plants are excellent choices in a Cardinal Tetra tank as they can survive in the same water conditions.

You can place other decorations as rocks and driftwood. You can also lay down some tree leaves to add some color and a natural feel to the tank.

One point to consider, though, is maintaining an open swimming space. Cardinal Tetras love to swim unhindered in the middle and upper water layers. So, place your plants at the sides of the tank and leave the central area free of any decorations and obstacles.

Finally, make sure that your current levels are very gentle so that the tetras aren’t buffeted around. Strong currents will bother and stress them and can even make them fall ill.

Diet & Feeding

Feeding Cardinal Tetras is very easy as they are omnivores and will eat practically anything you give them. In the wilderness, they are primarily carnivorous and feed on smaller creatures like insects and crustaceans. However, you can’t maintain this diet when they’re in the tank as they’ll refuse to eat dry food flakes or pellets later on if you only provide them with live food.

That’s not something you want, as they have a high vitamin requirement that is easily supplemented by dry food. Also, dry food is much cheaper and easier to come by than live or frozen food. 

So base about 75% of their diet on dry food and give them live or frozen treats periodically. Some protein-rich snacks include bloodworms, brine shrimp, fly larvae, insect eggs, as well as water fleas like Moinia and Daphnia. You can even give them blanched vegetables for more variety every now and then.

In general, Cardinal tetras should be fed several times a day, and any food that remains in the water after 2-3 minutes should be promptly removed to avoid overfeeding and water contamination. Also, always take care that all the food is small enough for the tetras to swallow.

Cardinal Tetras Behavior & Compatibility

Cardinal Tetras are very peaceful and mild creatures. They are very energetic and active during the day, where you’ll see them swimming as a group, exploring the tank, and feeding together.

However, when placed in a group of less than six, they become fearful and shy. They’ll spend most of their time hiding away and will eventually lose their bright colors. The expression of “The more, the merrier” is spot on in the case of Cardinal Tetras.

The tetras’ non-violent nature and the fact that they mind their own business make them great additions to community tanks. Yet, they can only be placed with fish that are non-aggressive and of the same size. 

Cardinal Tetras won’t be able to defend themselves when approached by territorial or large fish. Even peaceful fish might accidentally swallow the tetras. So, avoid fish like Rainbow Sharks, Goldfish, and violent cichlids.

Good tank mates for Cardinal Tetras include other tetra species like Neon, Green Neon, Ember, Black Skirt, and Emperor Tetras, to name a few. 

Zebra Danios, Chili Rasbora, Dwarf Gouramis, Guppies, Hatchetfish, and Mollies are also good options. So are Angelfish, small Catfish, and Otocinclus. Most loaches, dwarf shrimps, and snails make for great tank mates if you want creatures other than fish in your tank.

Breeding Cardinal Tetras

Breeding Cardinal Tetras is a very complicated and challenging process that will give any experience tank-owner a run for his money. That is because very particular conditions have to be met for the male and females to breed successfully.

For breeding to occur, the fertile male and female have to be isolated from their group and placed in a separate tank with well-regulated water conditions. This tank should have very soft and acidic water with a pH range of 5-6 and almost no light because eggs and the baby fish are very sensitive to light.

The female travels among plants and lays 150-500 eggs throughout the night. The male swims next to her, doing his part in fertilizing the eggs. Once they’ve finished, they should be promptly removed from the tank as they can eat the eggs.

In 24 hours, the eggs hatch and feed on the egg sac for five days. After that, they’ll start swimming, at which point you should start feeding them infusoria, rotifers, commercial fry food, and newborn brine shrimps. The baby tetras will start looking like their parents in about 2-3 months and reach their full size in 1 year.

Keeping Cardinal Tetras

Cardinal tetras are beautiful creatures and well worth any effort you put into raising them. As long as you provide them with suitable conditions and diets, you’ll see them grow and flourish before your eyes.

We hope this guide has helped you understand the needs of a Cardinal Tetra and that you’ll take the step in becoming a Cardinal Tetra owner.

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Christopher Adams
Hey there, my name is Christopher and I'm the creator and editor of this site. I've owned successful aquariums for the past 23 years. My mission is to educate, inform, and entertain on everything that's fish.

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