General Information
The Cardinal Tetra (Paracheirodon axelrodi) is a freshwater fish that thrives in tropical water and originates in South America. Cardinal Tetra fish are native to the Amazon basin in South America, mainly the upper Orinoco and Negro Rivers.
Cardinal Tetra Lifespan
The lifespan for a Cardinal Tetra is around 5 years if cared for accordingly.
In the wild most Cardinal Tetra only survive for about a year.
Please keep in mind that caring for an animal for such a long time is a big commitment and consider if you really want and can do that.
Appearance
Cardinal Tetra Size
Cardinal Tetra fish are a small species, and they generally grow to between 1.5 inches (3 cm) to 2 inches (5 cm).
The final size of an adult Cardinal Tetra also depends on the genetic and the type and amount of available food sources. The more food is available, the more the animal will max out on its potential growth.
Make sure to provide adequate food for your Cardinal Tetra, but don't over- or underfeed as this brings its own problems. You can find more information on feeding below.
Cardinal Tetra Colors
Cardinal Tetra have a horizontal blue stripe and a horizontal red stripe beneath. Both stripes run across the whole length of the body, which differentiates them from Neon Tetra, whose red stripe only starts in the middle of the body and extends to the tail.
Cardinal Tetra Shape
The bodies of Cardinal Tetra are small, slender and spindle shaped. The have eight translucent fins in total (dorsal, adipose, tail, anal, two pelvic and two pectoral fins). The head is rather small and round with non-bulging eyes and a small mouth.
Water and Tank Requirements
Cardinal Tetra Water Temperature
Cardinal Tetra are tropical water fish, which means
they thrive in temperatures between 72 °F (22 °C) and 81 °F (27 °C).
You may need to install a heater in your tank depending on what your usual room temperature is. Tanks without a heater will most likely have a similar water temperature as the surrounding air.
It's best to install a thermometer in your tank to check the temperature regularly.
Cardinal Tetra Water Parameters
The water quality should be maintained within a pH range of 5.0 - 7.0. Some sources state that it's possible to make them get used to alkaline water with a ph level of 8 or 9, but this is definitely not advisable as this is guaranteed to take a toll on their health, resiliance and longevity.
Cardinal Tetra Tank Size
Every Cardinal Tetra should have at least 1 gal (5 l) of water to themselves. So, if you want to keep 5 small Cardinal Tetra, there should be at least 7 gal (25 l) in your tank.
Please keep in mind that your aquarium hardscape also takes away from the overall water volume in your aquarium and that if you plan to add other fish to the tank you need even more water!
The calculated water amounts shouldn't be shared between species but always added up.
Cardinal Tetra Tank Requirements
Cardinal Tetra fish spend most of their time in the middle section of the aquarium. They feel most comfortable with dark substrate layers and the options to hide in shady spots. Light sand and stones as the ground layer and very bright lights without the possibility to hide might stress them considerably.
Behavior and Tank Mates
Cardinal Tetra are friendly towards their own and other species. This means they can be housed with other types of fish that are also generally friendly and have similar water and tank requirements.
Please note that even the most peaceful species can get aggressive when they feel threatened, e.g., when there is too little space in the tank or they have to fight with others for a limited food supply. Please always make sure to meet the requirements of your animals as closely as possible to avoid such issues.
They should be kept in groups of at least 6 animals. If kept in a smaller group they might get anxious and lethargic.
Cardinal Tetra fish are a schooling species. When they're uncomfortable they tend to stick closer together and only branch out when they feel more safe. They are peaceful and get along well with other peaceful animal species, they will sometimes even school with Neon Tetras.
Fish that are more aggressive, like angelfish or betta fish, will most likely harrass or even attack Tetra and cause them to be stressed and school almost constantly. It is therefore advisable to keep Cardinal Tetra only with other peaceful fish like guppies, dwarf gouramies, corydoras, plecos or mollies. Only experienced hobbyists could try putting a betta fish in an established Cardinal Tetra tank that is big enough for both species to have their own space while monitoring their interactions closely.
Cardinal Tetra are an active species that like to swim a lot, especially during the day. They enjoy floating plants for shade and like to explore between plants and in caves. They get intimated by bigger fish quickly and will probably most likely shy away from their owners.
Fish generally don't sleep the same way mammals do and how exactly they sleep is still a topic of research. It is clear though, that they also have periods of rest where they move less and their metabolism is reduced.
Feeding
Cardinal Tetra usually feed on small worms and crustaceans in the wild but are omnivores and will accept a wide variety of foods. Make sure to use food that is small enough for them to eat. You could for example use small flakes or granulate. It's important not to overfeed cardinal tetras, as they have small stomachs and can easily become constipated. A good rule of thumb is to feed them small amounts two to three times a day, only giving them as much as they can eat in a few minutes.
Breeding
Cardinal Tetra need enough clean water and nutrition to reproduce. Breeding cardinal tetras can be challenging and requires specific water conditions and attention to detail. They require soft, acidic water with a pH of around 5.0-6.0 and a temperature of around 78°F (26°C).
A separate breeding tank is recommended, as adult fish may eat their own eggs or fry.
During breeding, the male will chase the female and perform a "zig-zag" dance to stimulate her to release eggs. The female usually spawns between 100 - 500 eggs in the late afternoon or evening. After spawning, the parents should be removed from the breeding tank to prevent them from eating the eggs or fry.
The eggs look like tiny white dots and will hatch in about 24-36 hours.
The fry will be free-swimming after 4-5 days and are very light-senstitive, which means you should use floating plants and low light in the breeding tank.
Common Problems
- bullying: Cardinal Tetra are so peaceful that they won't do much to defend themselves when bullied by other, more territorial fish. Therefore it is crucial to only keep them with other peaceful species that will leave each other alone. Good tank mates are other small fish like tetras, rasboras, dwarf gouramis, danios and corydoras catfish..
- neon tetra disease: Although the disease is named after Neon Tetras, it can also affect Cardinal Tetras. When infected they will lose their color, have trouble swimming and develop cysts. The disease is deadly and can spread to other species, so prevention is crucial. Infected or dead fish should be quarantined or removed immediately and you should make sure to only feed proper and clean food.
- infections: Cardinal Tetra are also prone to other infectious diseases causing itch or fin rot. It is important to regularly check the water parameters, keep a clean tank and react immediately when spotting an infected fish. A healthy diet and the presence of healthy nutrients and bacteria (such as Bacillus subtilis) can boost their immune system further..
Fun Facts
- coloration: Cardinal Tetra have very vibrant colors that change according to light intensity. In bright light they will look almost fluorescent but when the aquarium lights are off, two reflecting blue spots on the front of their head will become visible..