Freshwater Fish

Pregnant Guppy Fish: How To Know And What To Do

Learning to tell if a guppy fish is pregnant is not a challenge. All it takes is a basic understanding of their biology and knowing what to look for! This guide will teach you what a pregnant guppy fish looks like and also give you some tips on how you can prepare yourself if the miracle of life comes to your aquarium.

How to tell if a guppy is pregnant

Guppies are popular life carriers with a penchant for constant breeding when conditions are right. There are many ways to tell if you have a pregnant guppy on your hands. However, various health conditions can create similar symptoms.

As a result, it’s easy to mistake sick guppies for pregnant ones. Here’s how to tell if a guppy is pregnant and not sick.

You witness the mating

One of the easiest ways to know for sure that you have a pregnant guppy is to see the mating process firsthand.

Guppies are not shy about breeding. While other species require precise water parameters and environmental conditions, guppies are a bit more flexible.

Many aquarists end up with babies without any direct intervention! In other words, if you have males and females in the same tank, mating is very likely to occur.

So how does breeding with guppies work?

Well, these freshwater fish are carriers of life. That means the eggs develop inside the uterus before the female gives birth to fully formed babies. This fact is important because it affects the way the fish reproduce.

Author’s Note: Insemination occurs inside the body, so don’t expect to see the female lay eggs like other species would.

When conditions are right, the males will start the mating process by chasing the females around the tank. The mating ritual can last several minutes, but the act of insemination is short and easy to miss.

As the male approaches, he will extend his gonopodium. The gonopodium is a modified anal fin that looks like a thin rod. He inserts the gonopodium into the female’s anal canal to pass a sperm packet.

You may see this act happen a couple of times as the male makes sure he successfully inseminates the female.

After that, everything is business as usual!

Mating is a quick process that most aquarists don’t even notice, and those lucky enough to do it tend to mistake it for aggression. However, once you know what you are looking for, you can easily recognize the behavior and use it as a telltale sign of a pregnant guppy in the coming weeks.

There are changes in the appearance of the gravid spot

The gravid spot is a unique physical characteristic that is exclusive to females in life. It is the darkened skin of the uterus located just behind the anal fin. The area is usually visible on female guppies, pregnant or not, due to their semi-transparent belly skin.

When the eggs are successfully inseminated, the babies begin to develop at the site of gestation.

In turn, you should see noticeable changes in the appearance of the stain. It will become more prominent and darker as those babies grow. Just before birth, the area is practically black.

Author’s Note: As you near the end of the gestation period, you may even see small dots at the gravid point. Believe it or not, those spots are the eyes of the babies inside!

belly gets bigger

Like most pregnant creatures, female guppy fish will increase in size as the pregnancy progresses. The size change does not happen overnight. It is a slow process that takes several weeks.

Female guppies are already a bit fat, but the size gains due to pregnancy are a bit different. In particular, the belly begins to swell.

It can even take on a somewhat square shape. Just before the pregnant guppy gives birth, the belly may even look somewhat angular.

There are other reasons why a guppy’s belly might get enlarged. Conditions like dropsy and swim bladder diseases could be to blame.

Pay attention to that gravid dot! That is the most apparent difference between a sick guppy and a pregnant guppy.

Observe behavior changes

The signs of pregnancy are not just physical. Many pregnant female guppies also begin to show behavioral changes.

The females tend to become quite aggressive when they are pregnant. While they can display combative behavior towards any fish that gets in their way, pregnant females tend to direct most of their anger at males.

That’s because males will often keep trying to mate with her even after she’s pregnant.

Aggression usually begins with females chasing males. If it progresses, the females might even resort to fin nipping!

As the gestation period ends and the fish is about to give birth, you will notice some more extreme behavioral changes.

The first is a new aversion to food. A guppy tends to avoid eating shortly before birth. If they eat, you may see them spit out the food later.

The pregnant female will also start looking for places to hide. She will go missing in action as she tries to find a peaceful place to give birth.

Author’s Note: Guppies are vulnerable to attack when giving birth, so they seek out quiet areas to avoid problems with other fish. Not only that, but more spread out parts of the tank improve the babies’ chances of survival.

Towards the end of pregnancy, guppies will also go through some involuntary actions. They include shortness of breath and body convulsions.

The length of the gestation period

The gestation period of guppy fish is not very long. On average, babies develop in the womb for about 21 to 31 days. In some rare cases, gestation can last up to 35 days.

Several factors will determine the exact range. Everything from water temperature to food availability will come into play. The same goes for the general health of the fish.

The actual birthing process is much shorter. It only lasts between two and six hours.

It is important to maintain good tank conditions when caring for pregnant guppies. Incorrect water parameters could delay the gestation period. In severe cases, environmental factors can terminate the pregnancy altogether.

Keep tank clean and check conditions regularly. Guppies can give birth under standard tropical aquarium conditions, but things must remain stable to ensure the health of the mother.

How many babies can you expect?

The number of babies you will have will depend on many different factors. Pregnant guppies can give birth to between 10 and 50 baby fish!

Genetics, food availability, the mother’s health, and a bit of luck will determine the exact number.

Age is also an important factor. Younger fish giving birth for the first time tend to have fewer young at first. The fry are usually smaller and weaker as well.

As she grows older and continues to mate, the female guppy usually has more and more babies with each pregnancy.

Now, there are no guarantees on the survival rate. Some babies are destined to die shortly after birth. Whether from being eaten by other fish or natural causes, getting a 100 percent survival rate is rare.

Some babies can even be born dead.

Again, the age of the mother is a big determining factor. Older fish with some experience tend to have smoother pregnancies than those that are still young.

Author’s note: An impressive fact is that guppies can get pregnant quite quickly after giving birth. Females can have a new batch of babies every month! Regular breeding fish can easily give birth to over 2000 babies in their lifetime!

How to Prepare for Baby Guppies

If you want to maximize your survival rates, there are a few steps you need to take to prepare for your next delivery.

Once you can tell that the female guppy is pregnant, consider moving her to a separate breeding tank. This is not a requirement, but it can make a big difference.

Being separated from the rest of the fish will greatly reduce stress. Also, it will give the babies a chance to fight for survival.

You don’t need a massive breeding tank. In fact, a small 10 gallon aquarium will do.

Alternatively, you can use a brood box within a larger tank.

Whatever you do make sure the babies have a way to hide and keep from being eaten. Even the mother will try to eat her young.

Many brood boxes have sloping bottoms so the fry fall down after emerging from the womb. You can also invest in some breeding mesh.

Fine-leaved plants also work well. Plants such as Java moss, guppy grass, and guppy grass provide plenty of cover and security for the fry. Many aquarists even see decent survival rates with these baby plants hatching in community tanks.

When they emerge from the womb, babies are usually curled up into a ball. The healthy will start swimming after sinking to safety. Remove any stillborn to keep the rest healthy.

To keep those babies well fed, you need to make sure you have the right food on hand.

Guppies are considerably larger than most fish that hatch from eggs. As a result, they can eat larger foods from the womb.

The best food is brine shrimp. It is high in protein and fat, so prepare a batch just before the mother gives birth.

You can also grow infusoria. As a last resort, powdered fish food is also suitable.

Be prepared to raise the guppies separately for about two to three months. At that point, they are sexually mature and ready to join larger community tanks.


As you can see, there are several easy ways to tell if a guppy is pregnant or not. After reading this guide, you shouldn’t have any problems!

Let us know if you have any other questions about the process or if you need help determining whether or not you have a pregnant guppy. We are always happy to help.

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