How Long Do Cardinal Tetras Stay Pregnant? Gestational Period And More!!

Cardinal tetras are a common type of freshwater fish that comes from the Amazon River basin. They’re famous for their bright colors and peaceful nature. But they also have some breeding behaviors that many pet owners aren’t aware of. This article will go over how long cardinal tetras stay pregnant during pregnancy and what to expect during this time.

Cardinal tetras typically stay pregnant for around 28 days or about four weeks. However, they are an egg-laying species that doesn’t interact much with their offspring once they’re born. Hence, it’s crucial to ensure proper tank conditions before the cardinal tetra breeding process begins.

In this blog post, we will be discussing How Long Do Cardinal Tetras Stay Pregnant? It is a common question that many people have. However, in answer to that question, we first need to answer a few other questions.

How Do Cardinal Tetras Reproduce?

Cardinal tetras are egg layers and live in huge schools with a female to male ratio of about one to three.

A few males will be dominant and breed with the females, while others may bully or force themselves on certain fish that they want as their mate. The breeding pairs stay together for most of the year, if not throughout it. However, after spawning, the female will become very aggressive and chase away her mate.

The male cardinal tetras fertilize the eggs. The males may still stick around to protect their offspring until they are strong enough to leave their parents’ territory.

While most fish only lay eggs once per year, some reports say some cardinals can spawn all year round.

When Be Will Cardinal Tetras Pregnant?

This is the most common question among fish hobbyists. The answer to this question depends on many factors, including temperature, water parameters, and even genetics of an individual Cardinal Tetra.

Usually, in the natural habitat of cardinal tetras, they spawn once a year. However, in some cases, this can also occur twice a year. The first spawning activity usually occurs between March and May, while the second one is during October to December of each year.

If you want to keep Cardinal Tetras as pets at home, it would be better not to mimic their natural habitat. However, if you do so, it can be challenging to determine when they will become pregnant and give birth to babies.

How Long Do Cardinal Tetras Stay Pregnant?

When it comes to the pregnancy of cardinal tetras, you will find that they are very similar to guppies. The gestation period for cardinal tetras is around 30 days. During the pregnancy, you will notice that they are continuously pregnant until their eggs hatch. At this point, you should separate the fish from the other fish. This will ensure that the parents do not eat their baby and protect the eggs from other predators.

After the female lays all the eggs, the babies from the cardinal tetras will start to hatch. You mustn’t feed them until they are entirely free swimming and on their own. Feeding too early can cause a lot of problems with your baby fish’s health.

How Often Do Cardinal Tetras Get Pregnant?

Most cardinal tetras will spawn once a month and lay around 100 eggs. During spawning, female cardinal tetras will release their eggs into the water. Male cardinal tetra fish then fertilize them by releasing sperm over top of them.

This process results in baby fish hatching out of these eggs about a week later if everything goes well. However, depending on how often you breed your cardinals, the female fish may release eggs and spawn again only a few days later.

So, Cardinal tetras can get pregnant multiple times in a row. In a year, they can breed up to three times.

How To Stop Cardinal Tetras From Getting Pregnant?

There are several things you can do to stop cardinal tetras from getting pregnant. First, make sure that they don’t have any other fish in their tank with them. Also, be careful when adding new cardinal tetras into the aquarium, or else they might end up mating. Finally, if you want to stop cardinal tetras from breeding, make sure they have a varied diet. This will help them live longer and stay healthier.

Finally, there are “breeding traps” that you can buy at the pet store. You put these in your tank. When a female cardinal tetra swims into it, she will stick on it and stay there until you remove her from the trap.

How To Know Cardinal Tetras Are Pregnant?

You can know when your female cardinal tetras are pregnant from the visual changes in their bodies. Some of the symptoms that Cardinal tetras show during pregnancy are:

Constant Gasping At The Surface Of The Aquarium Glass

Cardinal tetras will begin to gasp at the surface of your fish tank. This is because they are having difficulty breathing. So they need much more oxygen during pregnancy. It can be challenging for pregnant cardinal Tetra to get enough air from their typical gills.

Abdominal Distension

The Cardinal tetras’ belly becomes visibly larger. This is because pregnant cardinal Tetra is carrying eggs inside their bellies, which swell as they get closer to hatching time. So even though you can’t see it right away, this is a good sign that your female Cardinal tetras are pregnant.

Dark Bellies

A dark spot near their bellies occurs due to the egg sac, eventually holding the eggs in place under their tails. The spots can show up when they’re close to childbirth or after it comes out within 12 hours of fertilization, but before laying the eggs.

Mouth Breathing

Cardinal tetras will also begin to mouth breathe because they’re having trouble with their gills and need more oxygen than usual, like when you’re doing hard cardio at the gym. This is another good sign that your female cardinal tetras are pregnant.


Cardinal tetras also become more lethargic and less active than usual when they’re pregnant. This is because you should keep the eggs in a warmer climate. So the female cardinal Tetra will sit around in one place near a heat source (which can sometimes be your light bulb) for most of her pregnancy.

Trouble Eating Or Getting Food To Eat

Cardinal tetras also don’t get hungry as often when they’re pregnant. You may notice that your female cardinal tetra doesn’t get her usual appetite and will only pick at the surface of your fish tank, which is another sign she’s carrying eggs in her belly. This happens because the cardinal tetra has a pointed mouth and swollen bellies with eggs.

How To Know Cardinal Tetras Are Going To Give Birth?

It can be challenging to tell when cardinals are going to give birth. Generally, the gestation period for a cardinal is around 21 days. However, if you know what signs they have been exhibiting, then it becomes easier to determine that your other fish may soon have babies on their hands.

Some of the signs that indicate Cardinal tetras are going to give birth are:

  • They are swimming closer to the surface of the tank
  • Their bellies appear more significant than usual but not too big. If they seem to like their stomach is about to burst, it could be a sign that they will give birth soon.
  • Cardinal tetras stop eating and spend a lot of their time moving around for different spots in the tank.
  • They are acting more shy than usual.
  • They are chasing other fish away from their nesting sites.

If you notice that your cardinals have been acting this way, then it would be a good idea to give them some space and keep any tank mates away from the mother until after she has given birth.

Some FAQs

How Many Fry Do Cardinal Tetra Produce?

It is hard to know precisely how many fry do Cardinal tetra produce in one spawn. However, when you see them spawning, your cardinal tetra fish will usually lay around 150-500 eggs each time they generate.

What is the Best Tank Size for Cardinal Tetras?

The best tank size for cardinal tetra fish would be a 20-gallon long aquarium. This will give your female and male enough space to swim around and show off their vibrant colors, as well as keep them healthy and active.


Summing up, it is best to wait at least three weeks before expecting any signs of pregnancy. However, suppose you are looking for a more precise answer. In that case, it may be better for owners to contact their local fish store or veterinarian about the gestation period, specifically for cardinal tetras.

Hopefully, this post covered everything you need to know about how long cardinal tetras stay pregnant and got into some depth. I hope this will be very helpful in learning more information regarding the same topic discussed here today.

Scroll to Top