Can I Keep 5 Cardinal Tetras? | How Many Do You Need?

With their beautiful color, Cardinal tetras are one of the most popular fish in the aquarium hobby. It is primarily due to their attractive red and blue coloration, making them an excellent addition for almost any aquarium tank setup. Moreover, just because they are easy to care for doesn’t mean that everyone should keep 5 cardinal tetras.

But many things go beyond the ease to care, and keeping an ideal number of Cardinal tetras is crucial for their health. You must understand both overcrowding and under-crowding can cause problems.

So, can you keep 5 Cardinal tetras? Cardinal tetras are schooling fishes and need at least around six of them to feel comfortable. Any number lower than that, like five Cardinal tetras, will make them feel stressed out.

Further, there must also be an ideal ratio of male to female cardinal tetras in the aquariums. Less than one male for three females is not enough to keep them in good shape, and more than two males per female are no good, either.

Wait to know about the ideal size of Cardinal tetras in a tank? Then, read on to get your answer!

What Is The Ideal School Size Of Cardinal Tetras?

The school size of Cardinal Tetras is essential for their health. The ideal school should consist of at least six cardinal tetras but no more than ten to fifteen fish. If you want to keep larger schools, consider adding other types of tropical freshwater fishes instead or in addition to the cardinals. It will provide them with plenty of space to swim.

If you want to add other fishes, be sure that their body shapes are different from the cardinal tetras. Cardinal tetras will not have enough space for swimming if all of them have similar body shapes. Also, make sure that your tank is large enough and add a school of at least six cardinals instead of three or four.

Can You Keep 5 Cardinal Tetras?

Usually, it is not good to keep less than six Cardinal tetras because they are schooling fish. But some aquarists still insist on keeping the fewer fish and are pretty successful in this.

Also, many people would love to have a school of fish in their tank, but it depends on what type of setup they have. Some fish don’t mix well together, and others require certain water conditions. So first, you need to decide whether or not your aquarium can handle five cardinal tetras. If you only keep one tetra, then you probably don’t need to worry about it.

However, if you are new to fish keeping and want to keep Cardinal tetras, it is better to opt for six fishes for lesser complication.

Things To Consider When You Keep 5 Cardinal Tetras

Cardinal tetras are low-maintenance fish that do not need a lot of things to live peacefully in your aquarium. But since Cardinal tetras are schooling fish, keeping 5 Cardinals needs a little bit of attention and effort.

Some of the things that you must consider when you keep 5 Cardinal tetras are:

Size Of Aquarium:

You must have enough room in your aquarium to keep at least five Cardinal tetras. The minimum size of the fish tank should be 20 gallons or larger, although 30-gallon tanks are ideal for keeping Cardinals since they need space and open waters to swim around freely.

Aquarium Water:

For Cardinals to stay healthy, they must have balanced aquarium water. Cardinal tetras are sensitive fish that cannot live in waters with high pH levels or alkalinity levels. You can keep the ideal pH level of your aquarium between five and seven by using an acidic conditioner. Also, make sure that there is ample oxygen in your aquarium because Cardinals need water with high dissolved oxygen to thrive.

Temperature Of Aquarium:

You must maintain the temperature level of your Cardinal tetras’ tank between 24 and 28 degrees Celsius or 75 to 82 degrees Fahrenheit at all times. If you fail to keep the temperature right, it will stress your fish and make them sick.


You cannot keep Cardinal tetras with other fish with similar body shapes, such as Tiger barbs or Gourami. These fishes will not give Cardinals enough space to swim around freely, and they may also nip at their fins. If you want to keep Cardinal tetras with other fish, make sure their body shapes are different.

The best tankmates for Cardinal tetras are other Cardinal tetras, Harlequin rasbora, and Emerald dwarf rasbora.

Tank Decorations:

Cardinal tetras are schooling fish, so they like to swim in open waters where they can quickly move around their aquarium tank freely. Therefore, you should provide your Cardinal tetras with decorations that will allow the school of Cardinals to stay close together throughout their time in the water tank.

Place driftwood, rocks, and roots in the tank to give Cardinal tetras a place to hide. You can also use artificial plants for decoration that will make the aquarium look natural.

Foods To Eat:

Cardinal tetras are omnivorous fish, meaning they eat both plants and animal matter. In the wild, Cardinals feed on insects, worms, small crustaceans, and vegetation such as algae or leaves of plants.

Since Cardinal tetras are schooling fish, you must provide all members in the school with food at once rather than one by one to ensure that they get enough nutrients every day since they will eat up everything when they see food.

Live Plants:

If you want to keep live plants in your aquarium, Cardinals can be a good choice since they do not eat plants at all. But make sure that there are no sharp or rough edges on the leaves of the plants. Cardinal tetra will cut themselves and might even bleed to death if sharp edges of a plant catch their fins.

Ration Of Male And Female Cardinals:

The male Cardinals will fight each other when you keep them in an aquarium tank, which is ideal for more females than males. Also, remember that the ratio should be three or four female Cardinal tetras for each male fish.

If there are only two Cardinals of the opposite sex, they might breed and raise a family together. Thus, this can stress out your Cardinals.


How Long Will Cardinal Tetras Live?

Cardinal tetras have an average lifespan of about five years if you take care of them properly. But you should always be aware that the more Cardinals you keep, the higher chances for one to contract a disease and die. And this might leave your other fish vulnerable as well due to stress and overcrowding.

Do Cardinal Tetras Get Sick Easily?

Cardinal tetras are susceptible fish. So, they can get sick quickly and die if you fail to take care of them properly.

Therefore, if you want your Cardinals to stay healthy and live a long time, you should provide them with the right temperature level for their aquarium tank and a balanced water environment where there is enough oxygen for them to breathe.

Can I Put Cardinal Tetras With Other Fish?

Cardinal tetras are not aggressive fish. So, you can keep them with other freshwater or community aquarium fish as long as they will not bully the Cardinals around. But make sure that the water temperature is suitable and there is enough space for all of your school of Cardinals.

Can I Keep More Than One School Of Cardinal Tetras In My Aquarium?

Cardinal tetra is a schooling fish, so it does best when you put in more than one school of cardinals together. Then, it will make them happy and healthy throughout the years.

But remember that if there are only two Cardinals of the opposite sex, they might breed and raise a family. Thus, this can stress out your Cardinals if you did not ask for that.

What Is The Best Tank Size For Cardinal Tetras?

The best tank size for Cardinals is about 20 gallons of water. But always remember to provide them with more space than they need. So there have been no overcrowding problems throughout the years.


Summing up, keeping five Cardinal tetras in your aquarium is possible. However, the tank should be at least about 30 gallons in size with a heater and filtration system to keep them healthy. The pH level of your tap water will also affect how well they do, so you may want to test it before adding any fish or plants. Also, make sure that there is plenty of live (or fake) plants in the tank for them to hide.

Due to their small size, they are usually good with other community fish that do not nip at their fins or pick on smaller ones. Just be sure that there is plenty of hiding places, and territorial disputes will probably occur but shouldn’t cause any severe injuries between them.

I hope you found this article helpful and now know if you can keep five Cardinal tetras in your aquarium.

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