Looking for a friendly, fun, and colorful little schooling fish for your aquarium? Meet the Cardinal Tetra. These delightful little fish are great whether you’re a beginning hobbyist or long-time aquarist looking for an easy-to-care-for freshwater fish.

Quick Intro to Cardinal Tetras

Family: Characidae
Scientific Name:Paracheirodon axelrodi
Other Names:Neon red tetra
Care Level:Easy

Natural Habitat, Identification, and Where to Buy

In nature, Cardinal Tetras can be found in South America. While they have a wide distribution the two most common places to find them are the Negro and Orinoco rivers. The fish ranges as far West as Colombia and in northern Brazil. There are also reports of these fish living in the wild from where they either escaped from captivity or were dumped into the water.

The Cardinal Tetra is a freshwater fish known for stunning colors and fits great in a variety of aquariums. They are known for having a bright neon blue stripe that runs from their nose to their tail. Underneath the blue stripe is a bright-colored red stripe. The red color bleeds into the otherwise transparent tail. The underbelly of the fish is a white color that contrasts with the other colors of the fish. The coloring of both genders is similar enough that it can be hard to tell them apart by color alone.

This species of fish both looks and behaves similarly to their cousin the Neon Tetra. The main physical difference between Cardinal and Neon Tetra is that the Neon’s red stripe only goes halfway up their body and there is a less vibrant blue color. This fish is often bred in captivity because they are known for having simple husbandry needs.

This is a species of fish that likes community. In the wild, they will group in schools of fish that have upwards of hundreds of members. However, even if they are just kept in a small number in a tank, they will still move together as a school.

Optimal Water Conditions for Cardinal Tetras

Water Temperature:73°F to 81°F
Water Flow Rate:slow
pH:5.0 to 7.5 (below 6.0 is ideal)
Water Hardness:2 to 6 KH

Tank Setup

Minimum Tank Size: 20 Gallons per 6 fish, 2 gallons per additional fish
Optimal Tank Size:30 gallons per 6 fish
Optimal Tank Shape:Standard rectangular tank
Recommended Filter Type:Sponge filter with an air pump

This species of fish likes to leave in large groups and so it is important to have a tank that can hold a minimum of six. For six fish you will need at least a twenty-gallon tank, this will allow the fish to have enough space for how active they are. For adding additional Tetras to the tank, it is suggested of having two gallons per extra fish.

The most important part of helping Cardinal Tetra have good health is diet and maintain stable tank conditions. If these fish do not get the nutrition that they need they will start to lose their color and their immune system will suffer. It’s also important to make sure there are no rapid changes in the water quality or temperature because this can put the fish into shock and lead to a quick death.

In addition to stable water temperature and quality, the water needs to be kept clean. By doing regular water changes you can help prevent a buildup of harmful pollutants. Also, keep an eye out for algae buildups and make sure to remove it before it becomes a problem and harms the fish.

This species of fish prefer water that is incredibly soft and acidic. The pH needs to be between 4.5 to 7 and water temperatures that are between 73-81 Fahrenheit.

Creating the Landscape

When it comes to crafting the perfect fish tank, it is best to try and mimic the natural habitat as much as possible. This species tends to inhabit streams and shallow rivers that have a variety of vegetation.

This species of fish sticks to the middle of the aquarium. Despite this, the substrate that you put on the bottom of the tank is important. A lot of experts recommend using fine sand for the substrate because this will best resemble what is found on the bottom of riverbeds and still act as an anchor for live plants.

This species appreciates a mixture of submerged and floating plants. Suggested plants include Amazon Swords, Anubias, and Java Fern.

Make sure you leave an open area in the middle of the tank. While it is important to have vegetation so that it can block our light and offer shelter to the fish, the fish need the area to swim around.

Other things you can include at the bottom of the tank includes driftwood and rocks. Large chunks of driftwood work well because they can offer areas the fish can shelter in.

Best Plants:Amazon Swords, Anubias, and Java Fern
Best Lighting:There needs to be plenty of shade for the fish.
Best Decorations:Live plants, rocks, fine sand substrate, and driftwood.
Decorations to Avoid: Plastic plants.

Physiological Considerations for Cardinal Tetras

Size: up to 1.25 inches long
Lifespan:A healthy Cardinal Tetra lives four to five years.
Temperament:Peaceful
Preferred Tank Region:middle region
Scale Thickness:Nothing special to note.
Gill Considerations:Nothing special to note.
Swimbladder Considerations:Nothing special to note.
Fin Shape Considerations:Nothing special to note.

With the proper care, a Cardinal Tetra in captivity can live upwards of four to five years. This lifespan is dependent on several factors including genetics, a good diet, properly maintained tank, and water quality levels.

While this fish species is known for not being fussy and being hardy, the key to good health is to maintain stability in their environment. This need for stability means this fish is not the best choice for someone is who is brand new to fishkeeping. It would be better to pick a fish that isn’t as dependent on having precise tank settings kept.

The average length of a full-grown Cardinal Tetras is around two inches long. This small size allows them to be fit in several tank arrangements, including more compact tanks.

The fins on a Cardinal Tetra are transparent and normally they have white-colored bellies. They are known for vivid colors that have unique variations including silver and gold.

Society

Cardinal Tetras are like other tetras in that they are social fish that like to live peacefully in large schools. The minimum size school of Cardinals you should consider for your tank is six. Some fish experts suggest that a minimum group of Cardinal Tetras should include ten because they are more likely to have and show off vibrant colors. You can put this species in a community tank with other species if the tank and water settings are right and the other fish species are peaceful.

When looking for the right fish to place alongside your Cardinal Tetras, there are several other Tetra species that will fit perfectly alongside Cardinals. These Tetras include rasboras, danios, and dwarf gouramis. Other small fish that go well with this species include Pencil Fish, Dwarf Cichlids, Loricaids, and smaller rasboras.

Before looking at other species out of Tetras it is important to remember where the fish like to spend time. Cardinal Tetras like to move like a school together. They will zoom around the middle and upper levels of the tank. If you decide to add other fish species make sure they will not bother each other in the areas they like to swim and spend time, a crowded tank makes everyone unhappy.

If you are looking to branch outside the Tetra family there are a number of good tankmates to consider. While you can include medium members of the catfish family it is important to remember that you do not include a fish that is so big that it can swallow to the cardinal tetra. Make sure any larger fish are not aggressive or prone to attacks or nipping at fish fins or you may end up with hurt or killed fish.

If you have gotten as many fish as you want or can take over, there are other options for adding community to your tank. You can always add non-fish to the tank. When you want to add a variety of non-fish species it is important to make sure they are not aggressive or will attack or your fish (or vice versa). Options to consider include shrimp, snails, and crabs.

It’s important to find the right fish to get along with your Cardinal Tetras because community is such a big part of their lives. When you make their shoal bigger than they will be happier they will be. The happier your fishes are the healthier and long lived they will be.

Gender, Breeding, and Reproductive Considerations

There are a number of reasons this species is not recommended for first-time fish keepers; this includes the difficulty that comes from trying to breed them. It can be difficult to find a pair of cardinal tetras that are compatible. However, with some patience, perseverance, and hard work it is possible to achieve.

For those who are new to Cardinal Tetras, you may have trouble telling the difference between the male and females. This difficulty comes from the fact that they are only a few clear physical differences between the two genders. The females of the species have a slightly deeper body and round belly. The males tend to be on the slender side and have a hook that sticks out from the anal fin.

It can be difficult to breed Cardinal Tetras in captivity. In nature, Cardinal Tetras congregate in shaded regions located upstream when they are ready to breed. Most commercially bought Cardinal Tetras are caught in the wild and then shipped to be purchased at stores.

If you are determined to breed Cardinal Tetras it is best to utilize a breeding tank. This will allow you to remove the breeding pairs once the eggs have been laid and fertilized. If you do not remove the mating pair there is a chance the eggs or young fry may be eaten.

For a successful breeding tank, it needs to have the same water conditions are its natural habitat. The optimal breeding temperature needs to consistently stay between 75 to 90 degrees Fahrenheit. The pH levels of the water need to remain between 4.5-6.0, along with very soft water.

When setting things up for the fish to breed, you need to switch off the aquarium lights.

Water quality is paramount. There is a need to clean the tank daily and do weekly water changes so that the water parameters will remain stable during their mating. It is important to remove any pollution or algae before it begins to spread.

Another important step is to ensure your fish have a proper diet as they are getting ready to mate.

When the fish are ready to mate they will start swimming together and then move into the plants. The eggs they lay will hatch after three days. The fry needs tiny food like infusoria until they are big enough. Make sure the tank the fry are in has reduced light due to the fish having photosensitivity at that age.

Nutritional Needs

Cardinal Tetras are known for being willing to eat whatever they can get ahold of. In their natural habitat, they are omnivores. They will feed on worms and small crustaceans. Whenever they are kept in aquariums, they will accept fresh live food or regular flake food. As long as the fish are fed on a regular basis, they will remain happy.

It is recommended that you feed your Cardinal Tetras three times a day. Make sure that you give them only enough food that they will eat in a three-minute window. After your fish finishes, eating makes sure you remove the leftovers. If you do not remove the left-over food, it can fall to the bottom of the tank and begin to rot.

When deciding on what food to feed them, keep in mind these fish need a high number of vitamins. If you decide to feed them flake food, this means you will need to find a quality flake that will provide what your fish need. It is suggested that you either rotate through several types of flakes or even mix them together. By using several types of flakes you make it more likely your fish will have all the nutrition it needs.

Another option is using live or frozen foods. This can include some vegetables, just make sure to chop them up small enough for the fish to eat. In choosing live foods, mosquito larvae, adult brine shrimp and daphnia are all great choices. This species is also known to consume worms like blackworms and bloodworms.

  • Daphnia
  • Mosquito larvae
  • Adult brine shrimp
  • Blackworms
  • Bloodworms
Best Sustenance Food Type: A variety of dry, live, or frozen foods.
Additional Food For Optimal Health:Vegetables
Special Foods and Considerations for Best Color and Growth:No special foods, just keep a consistent and nutritional diet.
When and How Often to Feed Fish Based on Life Cycle:Feeding smaller meals three times a day

Common Diseases and How to Avoid and Treat Them

While this fish is known for being hardy, there are several diseases that need to be watched out for. The main diseases to look out for are common freshwater problems that most fish have. These ailments include dropsy, fin rot, and Ich.

These diseases are very easy to treat with using over the counter medication. The important thing is to monitor your fish for any illness and take care of them immediately. However, the best cure is prevention. Keeping your tank clean and maintained,  will drastically reduce the chance of the fish contracting a disease.

Another part of prevention is to perform regular water changes. When the water has been changed the next thing to do is to use a test kit in order to check on the chemistry of the water. Having a good filtration system will help stop the buildup of ammonia and nitrates in the water.

Before introducing new fish to your tank, it is important to check the new fish for any signs of disease. There is an illness called Neon Tetra Disease. This is a parasitic disease that gets introduced to the tank through new fishes that have had contact with infected fish, or it could be introduced by infection by consuming tainted food.

This disease has no known cure. It causes spinal issues, cysts, and various other health issues.

The only way to guarantee new fish will not introduce something deadly to your tank is to place newly acquired fish into a quarantine tank for a time of observation.

Best Antibiotics: Over the Counter freshwater fish antibiotics
Treatments to Avoid:Nothing of note.
Food Recommendations When Sick:Heavily nutritious food.
Hospital Tank or Isolation Withing the Community Tank:Just a basic tank with enough water.

5 Facts About Cardinal Tetras

  1. This species naturally comes from the South American regions of the upper Orinoco and Negro River drainages in Venezuela, Colombia, and Brazil.
  2. While many species grow larger in the wild, male cardinal tetras actually can grow up to twice as along in captivity as they can in the wild.
  3. Cardinal tetra eggs hatch between 24 and 30 hours after they’ve been fertilized.
  4. They have unique mating rituals with precise details. Female cardinal tetras release their eggs during rainy season around twilight.
  5. These fish release 500 eggs at a time for fertilization.

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