How Many Cardinal Tetras Can I Put In A 75 Gallon Tank?

Cardinal tetra is a beautiful little fish that has an iridescent stripe running along its light pink body. Because of their color, size, and peaceful nature, most owners keep them in community tanks with other small, non-aggressive species. However, if you want to put them together, it’s important to know how many of them can you keep into one tank. So how many Cardinal tetras do you think you can put in a 75-gallon tank?

In a tank of 75-gallon, you can keep around 30-40 Cardinal tetras. But this number depends on certain factors, such as the types of fish you hold with them, your cardinal tetras’ size, and their behavior. Along with this, you must also ensure that the tank has proper filtration, lightings, plants, and water conditions for healthy fish.

For any fish owners, you constantly need to deal with a lot of questions. So, this blog post will help answer these questions so that you can determine how many cardinal tetras to put in your tank.

How Many Cardinal tetras Can You Keep In A 75-Gallon Tank?

Cardinal tetra is a small species with an adult length ranging from two-and-a-half inches (63 millimeters) to three inches (76 millimeters). They are very similar in appearance to the Neon Tetras, but they’re slightly more extensive and less brightly colored.

Most aquarists aggress that the minimum tank size for cardinal tetra should be 20 gallons (75 liters), which can house up to five fish. However, it’s best to keep at least eight of them together to reduce aggression.

If you want to keep your cardinal tetras in a 75-gallon tank, then they can have up to 30-40 cardinal tetras. Along with this, the tank must contain decorations with plenty of hiding places and plants for them to retreat during aggressive periods. It’s also important that there are no sharp rocks or other objects in the tank, as they can damage your cardinal tetras’ delicate fins.

Is 75-Gallon Tank The Best Tank Size For Cardinal Tetras?

Yes, it is a good idea. The only thing you need to consider is that the tank has regular water cycling and the appropriate equipment. A 75-gallon tank is one of the best size tanks for cardinal tetras. A larger than recommended tank will be fine, but it’s important to remember that this fish still needs room to swim and grow.

Moreover, Cardinal tetras are schooling fish, so it’s best to keep them in groups of at least five fish. This is why you should choose a 75-gallon tank if it works for your home or office space. However, since this fish needs plenty of room when you keep them in schools, it is best to choose a bigger tank.

Cardinal tetras love to move around. They are very active fish. So, the more space they get to swim, the happier they will be.

What Are The Problems With Bigger Tank?

Undoubtedly, a bigger tank seems to be more comfortable and looks more beautiful. But a bigger tank is not always better for your fish and plants, which you should consider when planning to upgrade from a smaller aquarium to a larger one.

Moreover, some of the problems with the more giant tanks are:

Difficulty In Cleaning

A big tank with a lot of plants is tough to clean. You will need to spend more time and effort taking care of the plants, feeding them regularly, pruning their roots, etc. If you are not up for all that work, it’s better not to have any plants in your aquarium.

You Need A Powerful Filter

A bigger tank needs a more powerful filter than the one you use for your smaller aquarium. In addition, the flow rate of water in your tank should be at least twice lower than its filtration capacity so that it doesn’t suck up any living creatures or plants present there.

Tanks Are Not Good For Plants

Usually, big tanks are not suitable for the plants. This is because a bigger tank means a more significant number of fish and more waste they produce. It can be harmful to the plants if you keep them in there. Therefore, it is better to have a few small fish in your tank than keep many big ones.

Dangerous For The Fish

More giant tanks require more aeration and filtration, which can be dangerous for the fish if you don’t take care of them properly and regularly. Remember that more giant tanks also mean heavier equipment that may fall on the fish if you don’t attach it well.

Difficult To Set Up

Also, remember that more giant tanks can be more challenging to set up than smaller ones and the maintenance is also harder. It’s hard enough to clean a small tank, but imagine how much work it will take to remove all dirty stuff from your giant aquarium! So make sure you are ready for long hours of regular cleaning and maintenance before you upgrade your tank.

However, if you are new to fish keeping, managing a bigger tank is a good experience. Also, if you don’t mind spending more time and effort on your tank, then it’s better to have a bigger one than a smaller one.

Can You Keep Cardinal Tetras In 75-Gallon tank?

Yes, you can keep Cardinal tetras in a tank of 75-gallon or less. Usually, there is no set number for a certain amount of cardinal tetra fish per gallon because there are so many variables at play. The most important factor when looking into this topic is not the number of fish you have but the size of your tank.

Many variables can affect cardinal tetra populations, including:

Size And Shape Of Cardinal Tetras In The Tank

The size and shape affect the number of Cardinal tetras you can keep in a tank. Cardinal tetras are usually smaller fish with an average length of two to three inches. If you have a smaller or unusual-shaped tank, there is more room for the cardinal tetras, and thus they can be in larger groups.

Number Of Other Fish In The Tank

The number of other fish in the tank affects how many cardinal tetras there can be. Therefore, if you have more than one type of smaller fish in your tank, you need to consider their number before adding other fish.

The number of cardinal tetras in the tank automatically reduces when there are more fish in the tank. Therefore, sometimes your cardinal tetra population will stay steady even if you add them to the tank at different times. However, having too many small or timid fish is not a good idea since they prey on the cardinal tetras.

Lighting And Temperature

The lighting and temperature of your tank can affect the number of cardinal tetras you have in it, too. If the light is not strong enough, they will hide most of their time, which reduces their numbers since they cannot eat as much food when hiding instead of swimming around looking for it. Similarly, a tank that is too cold or hot will cause these fish not to do as well. Thus they cannot reproduce on the same level.

pH And Water Hardness

The pH and water hardness of your Cardinal tetras’ environment also affects their population growth rate since it affects how healthy they are overall.

Cardinal tetras prefer a pH of around 4.6 to 6.2. These fish cannot survive the water when it is too acidic or basic. When the water parameters are not suitable for them, then their swimming speed will reduce. 

Amount Of Food

The amount of food you give your fish will affect the number of cardinal tetras that can stay in your tank; if they are overfed or underfed, they may not live as long, resulting in overcrowding problems. So instead, you should try to give them just enough food to sustain the population.

Behavior Of Cardinal Tetras

If the cardinal tetras in your tank are constantly agitating or not as healthy, then there will be lower populations than usual. Therefore, in a tank with aggressive Cardinal tetras, it is better to keep them in smaller groups not to harm each other.


Summing up, the cardinal tetra is a prevalent fish in the aquarium hobby. Cardinal tetras are hardy, look tremendous, and school with other peaceful species when you keep small groups of six to nine individuals at home.

For best results, you can put about 15 Cardinal Tetras in a 75-gallon tank. That’s roughly one fish per ten gallons or so, which should be enough to keep your school healthy and happy.

Best of luck!

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