The Cardinal Tetra (Paracheirodon axelrodi) is a small tropical freshwater fish that is extremely popular and well known in the aquarist hobby.
Looking similar to and often confused with its cousin, the Neon Tetra, it has a diminutive size that works well for smaller tanks adding a flourish of vibrant color and shimmer that is exceptional.
These fish love to school and are easy to care for, so they are a favorite for newbies to the hobby too.
Native to South America, they are usually found in the upper reaches of the Negro and Orinoco rivers. Unusually for such a small fish, most that are available in the trade are actually wild-caught. They school in hundreds in the wild, which makes for quite a sight to behold if you’re lucky enough to see them in action.
Incredibly fun to watch in a home aquarium, most owners find they will spend an inordinate amount of time observing them and enjoying their active and mesmerizing behaviors.
Let’s cover how to best care for these fish, find their perfect setup, and ensure they have all of their needs met for a happy and healthy life.
Cardinal Tetra Behavior
These are very peaceful little fish who will not cause any sort of issues within a tank community.
In fact, you’ll need to worry more about who you add to the community on behalf of your Cardinal Tetras, as they are easy targets for bullying and bad behavior by other more aggressive fish.
This is key to know, as any such behavior towards these little guys will stress them out to the point that they lose their potent coloring, become reclusive despite their need for socializing, and even die as a result.
Active and energetic swimmers like most Tetras, your Cardinals will provide plenty of enthusiastic daytime action for observation, and their little personalities will really shine through. Is it any wonder they’re a fan favorite?
You’ll need a minimum of six to enable them to feel secure in a tank. They absolutely require a group to school with and to boost their confidence. The more you can have, the better for these fish, however. You should note that larger schools will help create more vibrant coloring in your tank gang too.
These fish as so peaceful, they don’t even get too aggressive when it comes to the breeding season!
The Nobel Peace Prize in your tank will go to the Cardinal Tetras!
Cardinal Tetra Lifespan
If you cater to the needs of your Cardinal Tetras, you could expect them to live for around 4 – 5 years. The quality of their tank conditions will impact their lifespan, as always, so you can expect a longer life if you meet their requirements meticulously.
We will discuss more on tank requirements a little later in this article.
Cardinal Tetra Appearance
Tetras, in general, are all about putting on a show in your tank. And for the hobbyist, it’s about having something truly special to show off to your friends and family.
Their appeal is, without a doubt, due to the brilliant color pattern that makes them a joy to look at and also easy to spot amongst the lush vegetation they require (more on that later).
As we mentioned earlier, these Tetras are often mistaken for their Neon Tetra cousins. It’s not surprising as they are similar in every way physiologically except for a key difference in the red striping they possess.
Both have the same body shape, size, silvery-white base body color, and metallic or neon blue stripe that runs the length of the body from nose to tail.
However, the Cardinal Tetra has a red stripe below the blue stripe that also runs full body length. The Neon Tetra has only half a red stripe that begins mid-body and runs to the transparent tail.
Fins as all small and predominantly transparent, and their scales are tiny and densely compacted, which gives them a luminescence in the tank second to none. These Tetras practically glow and radiate color.
Beyond that, they are almost identical, so you can be forgiven if you’ve misidentified some Cardinals as Neons before as the Neon Tetra is more commonly known outside of the hobby.
They have large eyes and reach up to about 2 inches in length. So small, but not a nano-fish.
Females are slightly rounder than males, which becomes more obvious around mating season. Males can be identified by a small hook on their anal fin that distinguishes their sex another way.
Cardinal Tetra Habitat And Tank Requirements
In the wild, these fish are found in predominantly blackwater, meaning that the water is clear but brown. This does not mean these fish like dirty water! The brown coloring comes from the tannins leaching into the river from all of the debris and rainforest wood that falls into the riverbed.
Blackwater usually involves a lot of tangled root systems in the water from the riverbanks as the vegetation is so lush. You can add tannins to the water by adding dried leaves, but they need replacing every few weeks. Your stockist can provide the right types of leaves to do this, so do not collect your own and think they will be okay!
Having the correct tannins in your tank will help keep the water slightly acidic, which is what these fish prefer.
Cardinal Tetra Tank Conditions
The ideal setup for these fish is something that has a natural look to it that has a stable temperature and parameters. Fluctuations are the bane of most fish, even though the conditions may be tolerable. Although they may tolerate a range of temperatures, it is not okay to have your tank have temperatures up and down within that range.
A heater and thermometer to monitor are ideal for keeping your tank on an even temperature keel as they are tropical fish.
Darker substrates and dim lighting will show off your tetras to their best. Sand or mud works best for these fish, and they will both offer a good base for planting live plants.
Floating plants are a good addition to dim the tank lighting levels for your Tetras too.
Some of the best-rooted plants to include in your setup are Amazon Swords, Java Ferns, and Anubias Nanas, which can be used in a variety of ways.
Rocks and driftwood occur naturally in their habitat and should form some of your decors.
You do need to be careful to avoid over planting and runaway plant growth that could detract from open swimming areas as these fish do need it to manage their activity levels.
In the wild, they are used to slow-moving waters, so avoid powerful filtration that will disrupt the water movement too much as they dislike it and can stress them out. Undergravel filters work exceptionally well to avoid this problem.
Water changes need to be done weekly at least 25 – 30% to keep optimum water quality.
Water conditions should be noted and maintained as follows:
- pH of 4.6 – 6.5
- Water hardness between 2 – 6 dKH
- Temperature between 73 – 81ºF (23 – 27ºC)
- Lighting conditions should be natural or dimmed and set to a daylight cycle
Cardinal Tetra Tank Size
The minimum tank size for a group of six Cardinal Tetra would be 20 gallons.
Since we don’t advocate that you keep one solo and they enjoy a group of a minimum of six in a tank, you will need that 20-gallon minimum and aim for more, adding another 2 gallons for every additional community member.
Choosing Tank Mates For Cardinal Tetras
When it comes to finding species appropriate for your Cardinal Tetras, you need to consider peaceful and slow-moving tankmates. They can’t escape bullying tactics and will be startled by fast-moving fish, which will only stress these fish out.
Some excellent tank mate pairings for your Cardinal Tetras that would work well include:
- Neon Tetras
- Danios
- Guppies
- Rasboras
- Dwarf Gouramis
- Opaline Gouramis
- Smaller catfish species
- Dwarf Cichlids
- Pencil fish
- Hatchetfish
- Angelfish
- Small Shrimp
- Crabs
- Zebra Loaches
- Yoyo Loaches
- Otocinclus
- Mystery Snails
Avoid anything aggressive like larger Cichlids, Barbs, and Bettas, who are known to be fin-nippers, or just biting other fish in general, which would render your Tetras in peril.
It’s also worth mentioning that even peaceful fish that are larger and not generally aggressive will absentmindedly eat these fish unprompted, so size matters, folks!
Feeding Cardinal Tetras
Cardinal Tetras are omnivores who are not fussy and will eat everything from flake and pellet foods to live or frozen diet sources.
Things that are higher in protein is their preference. You should supplement live or frozen sources regularly in addition to a high-quality low-grain flake or pellet food. Things like Bloodworms, Tubifex, Daphnia, and Brine Shrimp all fit the bill.
Higher quality foods will impact the coloring of your Cardinal Tetras too!
Blanched and finely chopped vegetables are also ideal to offer regularly to mix things up, but take to remove anything they don’t eat to avoid fouling the water.
Aim for a meal at least once per day, and ideally in quantities that amount to what they can consume in three minutes. Any longer than that and your fish will likely be guilty of overeating which is never a good idea.
Cardinal Tetra Common Diseases And Illness
Neon Tetra Disease is a pervasive disease for all Tetra species despite its name. This is a parasite that is often introduced into the tank via unquarantined fish or infected live foods.
Unfortunately, this is not a treatable affliction, so spotting it is important before they are eaten by any other fish or infect others. Removal of infected fish and euthanization is the only option.
The stability of water parameters is also very important for these fish. They do not handle temperature drops well, so a regulating heater is important if you want to have your Cardinals for a long and healthy lifespan.
The other typical well-known freshwater afflictions will impact Cardinal Tetras too. Things like Ich, Fin Rot, or Bloat are commonly spotted but are more easily treated when caught early.
Breeding Cardinal Tetras
For any hobbyist looking for a relatively easy breeding project, Cardinal Tetras are fairly straightforward. They aren’t often bred at home, but if you create the perfect conditions to trigger spawning, it can be very rewarding.
One thing you will require is a separate breeding tank since you’ll need to keep the temperature slightly elevated, lower the pH and adjust the hardness to between 1 – 2 KH to encourage breeding without disturbing the other fish.
Dimmed lighting is also a must to encourage spawning behaviors.
Females can spawn up to 500 eggs for fertilization, and if successfully fertilized, they should hatch anywhere between 1 – 2 days.
Adults should be removed from the tank to prevent them from eating the eggs or fry.
In about a week, the fry are free-swimming and can be fed infusoria and baby brine shrimp.
Even though the Neon Tetra is more commonly known, we think the Cardinal Tetra should be given a shout-out since they have an even more striking color pattern.
An easy to care for schooling fish, they will dazzle with their displays and delight anyone who spends time observing them.
Simple tank requirements, a class-act attitude, and vibrant good looks are what make Cardinal Tetras a dream fish for many in the hobby. Once you have them, it’s hard to imagine life without them.
Try taking on ‘The Other Tetra,’ and you won’t be disappointed!
