Cardinal tetra care guide

Cardinal tetra (lat. Paracheirodon axelrodi) are amazingly beautiful fishes and they are the most popular ones in aquarium husbandry. The most of the fish beauty can be seen in the fish school – in a thickly planted tank such a school looks especially glamorous.

When keeping cardinal in soft and acidic water (black water) the cardinal tetra coloring becomes more bright. Also fish looks quite fascinating in a thickly planted tank with soft lights and dark bottom substrate.

If your tetra inhabits in a tank with stable good conditions, it’ll live for a long time and it’ll resist diseases. But if the tank has unstable changeable conditions, the cardinal tetra dies very quickly.

Besides as well as a common neon fish the cardinal tetra is also susceptible to neon tetra disease (NTD). When fish gets ill, its coloring sharply turns pale. As we already mentioned, sadly, there’s no cure for disease.

Habitat in the wild

Cardinal tetra (lat. Paracheirodon axelrodi, Schlutz, 1956) is one of three representatives of Paracheirodon genus, that includes neon tetra (Paracheirodon innesi, Myers, 1936) and green neon tetra (Paracheirodon simulans, Géry, 1963).

In the wild these schooling fishes inhabit in the middle water layers of flooded forests and tributaries of the river Orinoco and Rio-Negro middle and upper basin. Huge overflow lands appear there during the annual flood rise and cardinal tetra just like many other fishes use these areas for feeding, breeding and shelter.

Since the floods begin tetras migrate upstream from the river tributaries to overflow lands and they come back only for the dry season.

The river “black water” is called so because the rotting plants evolve tannin into the water and it colors the water into dark brown (brew color).

As a result of high organic load the water has specific composition and properties. Inhabit in water with temperature +23…+27 °C, pH = 4,0—6,0 and hardness dH = 5—12°.

Scientific NameParacheirodon axelrodi
Common NamesCardinal tetra; red neon tetra
Range and habitatSouth America
Size2.5-3.0 cm (1-1.25 in)
Lifespan3-5 years
Ease of keepingMedium
Minimum tank size80 liters (20 gallons) and more
Temperature21–27 °C (70–81 °F)
Water hardness5-10 dGH


Female body length is up to 5 cm (2 in) and the male size is about 2.5-3.0 cm (1-1.25 in).

The cardinal tetra back is olive and beige, it has a neon opalescent bright-blue stripe that goes from its eye to the flesh fin, below this stripe there’s a wide bright-red stripe, the abdomen is whitish.

Cardinal tetra vs neon tetra

First of all they are different fishes, though cardinal tetra is sometimes called red neon tetra. Cardinal tetra is sufficiently larger and its red stripe goes through the whole lower body when neon tetra stripe takes only half of its body.

Cardinal tetra (left) and neon tetra (right)

Difficulties in keeping

Care is rather complicated, since the fish is more demanding than neon.

The thing is that tetra is very sensitive to water parameters and purity, if water parameters are changeable the fish tends to get ill and die. The cardinal tetra is recommended for experienced aquarists, since it rather often dies in a new tank of aquarists beginners.


The study of gastrointestinal tract contents of 80 species in the wild showed that they are micropredators. Food consists mainly from zooplankton and blood worm. The cardinal tetra is easy to feed, it’s not demanding and it eats all types of feed – live, frozen and artificial.

It’s important that the feed is small grained, because the cardinal tetra has rather small mouth, favorite food is blood worm and tubifex.

Care and keeping in a tank


In the wild, cardinal tetra lifespan doesn’t exceed two years, but if provided with proper care in a tank without starving or getting ill, it lives up to 5 years.

Tank size

Cardinal tetra is a schooling, active, and absolutely peaceful fish. You should get about 10 cardinal tetra and more since, in a school of this size, it is more active and less timid. It swims in a school and demonstrates better coloring. The capacity of a tank may be not large – for a school of 10 cardinal tetra species 15-20 gallons tank will be enough. The tank should have a lid since the fish is very active and can easily jump out of it.

Water parameters

You must maintain a comfortable water temperature of about 73–81°F (23–27°C). Once a week, you should renew 20% of the tank water. Optimal water parameters for keeping the fish are the following: 73–81°F (23–27°C), pH 6.0-7.0, GH up to 5.

Tank setup: decorations and plants

The lights should be of moderate intensity with lots of plants in the tank. It’s better to shade that tank with fluctuates. Although the fish needs to have some shelter in the tank, it also needs some open space for swimming.

A thickly planted tank with some free space in the middle will be an ideal one for such a fish. With the help of tank decorations, you can create many shelters.

When decorating the tank, it’s better to make it look natural, i.e., use natural decorations: stones and snags. It’s better to use sand or small pebbles as a tank substate. However, it doesn’t matter much for the fish. Cardinal tetras swim in the middle water layer, and they don’t pick up food from the bottom.

A school of cardinal tetras will look good in a sickly-planted tank. You can put the plants along the back and side walls of the tank and leave a space in the middle for the fish to swim. You can use any popular tank plants: amazon sword, cryptocorynes, hornwort, vallisneria.


Cardinal tetras are very sensitive to ammonia and nitrates content in the water, so we don’t recommend putting them into newly settled tanks without stable biological balance. The more stable the water parameters are, the more comfortable it is for the fish. You should install a filter of proper capacity in the tank, but no strong water flow is needed. It’s better to use a canister filter since bacteria living in it will decompose ammonia and nitrates into less toxic compounds.

Tank mates

Is a peaceful fish which just like all tetra fishes loves company. It’s desirable to keep a school of 10 species, this is the way they’ll show their best coloring in the tank and also feel comfortable.

The cardinal tetra will do for community tanks at the condition that water parameters are stable and tank mates are not troublesome.

Gender differences: male vs female

Gender dimorphism is very little pronounced as well as of other species of this kind. When total body size of tetra kept in a tank is 3.5-5 cm (in the wild it’s up to 2.5 cm) the female tends to be larger and fatter than male (especially during their spawning period).

The cardinal tetra becomes reproductive at the age of 9 month. In the wild lifespan isn’t more than a year, however in the tank the fish may live up to 5 years.


Breeding may be performed both in couples and in school. Usually there 2-3 males for 1 female in a tank. In case of the cardinal tetra couples breeding you may need a tank about 0,5 gallons capacity, if the breeding will be of schooling type the tank capacity should be about 1 gallon.

The water level in a spawning pond should be about 30 cm. Water hardness is 1-2°dH, since if the water is harder the eggs may not get fertilized; pH= 5 – 5,5 and water temperature about 24 -26 °C.

The water should be disinfected by means of ozonizer or ultraviolet lamp. The spawning net and plants with small leaves are put on the tank bottom.

In about a week before the spawning starts it’s desirable to put males apart from females. The cardinal tetra that are to breed are kept in the water with low temperature (about 22 — 23 °C) and fed high and well. You should stop feeding the fishes the day before putting into the spawning pond.

Sometimes the spawning process is delayed for about 5-7 days.

You shouldn’t feed the fishes in the spawning tank , though there’s no sense in keeping them there more than a week. If the eggs weren’t laid during this period of time, you have to remove the fishes from the spawning tank and a few days later try to make them breed again.

The spawning starts when it gets dark and it lasts for several hours. About 300-500 transparent orange eggs appear in the tank during this time.

The tank with eggs should be shaded, since they are very sensitive to light. In 20-36 hours larva appears from the eggs. They start to swim in 5-6 days after that.

As soon as the cardinal tetra juveniles start to swim you should start feeding them. Start feed for juveniles is infusorians and crustaceans nauplii. After you start feeding the juveniles in the tank, you have to start slow aeration of the water.

Also gradually make the water more hard, because it’s necessary for the juveniles. To do this it’s enough to add some water from the community tank into the spawning pond.

As the juveniles grow the start eating feed of larger size. During the first 2 weeks of their lives juveniles hide under the tank plants leaves.

During the 3rd week a blue stripe appears along their body. At about the age of 1 month and a half they have a shape and coloring the same as the adult cardinal tetra has and they can be transferred to the community tank.