How To Tell & What To Do…

Learning to tell if a guppy fish is pregnant isn’t difficult. 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 looks like and also give you some tips on how to prepare if the miracle of life ends up in your aquarium!

How to tell if a guppy is pregnant

Guppy fish are popular livebearers with a penchant for constant breeding when the conditions are right. There are many ways to tell you have a pregnant guppy on your hands. However, several health conditions can create similar symptoms.

As a result, it is easy to confuse sick guppies with 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 do not hesitate to breed. While other species require precise water parameters and environmental conditions, guppy fish are a bit more flexible.

Some pregnant guppy fish swimming with other fish

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

So how does breeding with guppies work?

Well, these freshwater fish are viviparous. This means that the eggs develop inside the uterus before the female gives birth to fully formed babies. This fact is important because it has an impact on how fish reproduce.

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

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

As the male gets closer, he will extend his gonopod. The gonopodium is a modified anal fin that looks like a thin rod. He inserts the gonopod into the female’s anal vent to squeeze out a packet of sperm.

You might see this act happen several times as the male makes sure he is successfully inseminating the female.

After that, it’s business as usual!

Mating is a rapid process that most aquarists don’t even notice, and the lucky ones who do tend to mistake it for aggression. However, once you know what to look for, you can easily recognize the behavior and use it as a telltale sign of a pregnant guppy fish in the weeks to come.

There are changes in the appearance of the gravid spot

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

When the eggs are successfully inseminated, the babies begin to develop in the gravid spot.

A pregnant female guppy with a darker gravid spot

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

Author’s note: As you approach the end of the gestation period, you may even see tiny dots in the gravid spot. Believe it or not, those spots are the eyes of the babies inside!

The belly grows

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

Female guppies are already a little plump, but size increases due to pregnancy are a bit different. Most notably, the belly begins to swell.

It can even take on a somewhat square shape. Just before the pregnant guppy gives birth, the tummy may even appear somewhat angled.

There are other reasons why a guppy’s belly can get bigger. Illnesses like dropsy and swim bladder disease could be to blame.

Watch out for this gravid place! This is the most apparent difference between a sick and pregnant guppy.

You notice changes in behavior

Signs of pregnancy aren’t just physical. Many pregnant female guppies also begin to exhibit behavioral changes.

Women tend to get quite aggressive when pregnant. Although they can show a fiery behavior towards any fish that gets in their way, pregnant women tend to direct most of their anger at men.

This is because males often try to mate with her even after she is pregnant.

Aggression usually begins when females chase males. If this progresses, the females might even resort to fin pinching!

As the gestation period ends and the fish is about to give birth, you will notice 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 might see them spit the food out later.

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

Author’s note: Guppy fish are vulnerable to attack when giving birth, so they look for quiet areas to avoid trouble from other fish. Not only that, but sparser parts of the tank improve the babies’ chances of survival.

Towards the end of pregnancy, guppies will also go through some unintended actions. They include labored breathing and body convulsions.

The length of the gestation period

The gestation period for guppy fish is not long at all. 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 overall 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 aquarium conditions when caring for pregnant guppy fish. Incorrect water parameters could delay the gestation period. In severe cases, environmental factors can completely terminate the pregnancy.

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

How many babies can you expect?

The number of babies you end up with depends on many different factors. Pregnant guppies can give birth to between 10 and 50 baby fish!

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

Age is also an important factor. Young fish that give birth for the first time tend to have fewer babies at first. The fry are often smaller and weaker as well.

As she ages and continues to mate, the female guppy typically has more and more babies with each pregnancy.

Now, there is no guarantee as to the survival rate. Some babies are doomed to die shortly after birth. Whether it’s being eaten by other fish or natural causes, it’s rare to achieve a 100% survival rate.

Some babies may even be stillborn.

Again, the age of the mother is a 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 guppy fish 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 2,000 babies in their lifetime!

How to prepare for baby guppies

If you want to maximize survival rates, you need to take certain steps in preparation for the upcoming birth.

Once you are able to tell the female guppy is pregnant, consider moving her to a separate breeding tank. It’s not a requirement, but it can make a huge difference.

Being separated from the rest of the fish will greatly reduce stress. Moreover, it will give the babies a chance of survival.

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

Alternatively, you can use a breeding box in a larger tank.

A pregnant guppy fish swimming in a large freshwater community tank

Whatever you do, make sure babies have a way to hide and avoid being eaten. Even the mother will attempt to eat her young.

Many breeding boxes have slanted bottoms for the fry to fall off after leaving the womb. You can also invest in breeding mesh.

Fine-leaved plants work well too. Plants like java moss, hornwort, and guppy grass provide ample cover and security for the fry. Many aquarists even see decent survival rates with these plants for babies born in community tanks.

When they come out of the womb, babies are usually curled up in a ball. Healthy people will start swimming after sinking safely. Remove all stillborns to keep the rest healthy.

In order for these babies to be well nourished, you need to make sure you have the right food on hand.

Baby guppy fish are considerably larger than most fish that hatch from eggs. As a result, they can eat larger foods right out of 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 adequate.

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


As you can see, there are a number of easy ways to tell if a guppy is pregnant or not. After reading this guide, you should have no more problems!

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

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