Fishbowl Adviser

How to Tell if Guppies are Pregnant

If you’re keeping or breeding guppies, you’re probably wondering how you can know if you have any pregnant ones. In case you have both males and females, chances are that they will have offspring any time soon. Guppies are very prolific breeders, and a single female can have around two thousand young in her lifetime. However, guppies tend to eat their offspring, so if you want to keep them alive, you’d have to learn to recognize a pregnant guppy.

guppy fish

How Can You Tell Male from Female Guppies?

The first step before you start looking for pregnant fish is to know to determine the sex of the fish. The difference between males and females is the following:

  • Males have longer bodies, they are often more colorful and have patterns on their wide caudal fins. They also have a longer dorsal fin.
  • Females are rounder, bigger, and have a gravid spot above the anal fin.

Only females can bear offspring, but there’s one interesting fact and a survival mechanism for guppies – up to a quarter of their offspring are fathered by a dead male. Females live much longer than males, so they sometimes store the sperm for up to a year and become pregnant multiple times from just one insemination. So, even if you had a male in your tank and he died, it doesn’t have to mean that the female won’t get pregnant by herself.

Guppies Are Live-Bearers

These popular freshwater fish don’t lay eggs. Unlike the majority of fish such as goldfish that can’t get pregnant and carry the babies in their bodies, guppies give birth to live fry. Just like humans, they have contractions, and they tend to breathe faster when they’re preparing to give birth. As soon as they’re born, the babies are in danger because they can get eaten by the female. Luckily, 30 to 60 babies are born in just one pregnancy, and that number can reach up to 200. The female can get pregnant a few hours after it just gave birth, and the babies become sexually active at six weeks. Having all this in mind, you might want to keep an eye on your guppies if you plan to have both males and females in the same tank. The mating happens fast, and you might not even see it. If you did, pay attention to the pregnancy symptoms to keep the guppy population at bay.

What Does a Pregnant Guppy Look Like?

Now that you know which ones are the females, and you’re suspecting that some of them may be pregnant, you can start looking for the following symptoms:

  • Their belly becomes swollen and bigger. A swollen abdomen is best visible when you compare female guppies with one another. The bigger it gets, the more it resembles the shape of a box. Also, a bigger belly means more fries.
  • The gravid spot above the anal fin becomes darker and more visible. Sometimes the spot even changes shape. It can be black or pink/orange, depending on the color of the guppy. The gravid spot is actually dark from the eyes on the babies inside of the belly.
guppies in aquarium

Their Behaviour Changes as Well

As the female becomes pregnant, you’ll see some other changes as well, such as behavioral ones. You will notice that they’re not as active, and they will often sit at the bottom of the tank. If you see a female isolated in the tank, or swimming in one place, it’s a sign that it’s about to give birth. It can also become more shy or aggressive and attack other males in the tank that are trying to mate with her. The female guppy can also start refusing food, and rubbing herself to the items in the aquarium like the wall or decorations. All of these changes begin around three weeks after the mating. If you see some of these signs, most likely your guppy will give birth in a week or so.

How Long Does the Gestation Period Last?

Very short – they give birth after 21 to 31 days after mating with a male, but this time varies and depends on many factors. Some of them are the conditions in the tank, the health of the fish, and the level of stress that the mother was exposed to. On average, the gestation period lasts anywhere from 22 to 26 days, and they can get pregnant once a month on average.

How to Care for a Pregnant Guppy?

Once you’re certain that the female is pregnant, and you realize that it’s about to give birth any time now, it’s time to start acting accordingly. If you’re breeding guppies and you care for the whole offspring to survive, you have to care for the pregnant female as well. That means minimizing all possible stress because she can miscarry or the babies can have a lower chance of survival. It is recommended to get a breeding box and to put the fish inside, but not for too long. Even though it’s the best solution, it’s also stressful for a pregnant female. Get the one with water circulation so the fish can breathe and put the female inside using a fishnet. If it doesn’t give birth in 24 hours, take it back to the tank, or try increasing the water temperature, as it can help with the birthing process. Keep the pregnant guppy isolated, well-fed and offer her a variety of food to avoid nutrient deficiency.

What to Do After Birth?

You can expect the guppy to give birth for two to six hours if she’s not stressed. If the female had any stress recently, the birth can last even up to twelve hours. If you see that the birthing stopped, return the fish into the community tank, because the isolation can stress her even more. A healthy female will give birth to one fry at a time, and she will make short pauses to rest.

Healthy fry is born curled in little balls, and they uncurl and start swimming very quickly. Stillborn or unhealthy fry will not move and it will sink. If you notice that happening, remove them from the tank. Feed the healthy fry five times a day with small-sized food such as baby brine shrimp and don’t put them in the community tank until they’re at least one and a half-inch long. This will ensure that the other fish don’t eat them. If there isn’t already plenty of space for hiding in the water, make sure that you put something where the fry can hide, such as floating aquarium plants. Also, feed your fish before you introduce the fry so that the bigger ones don’t welcome them hungry and mix them up for a dinner.



Guppies are very easy to take care of and they’re amazing for beginners. However, they’re very fertile, and if you keep males and females in one tank, you can expect their offspring very soon. Knowing when the guppy will give birth will guarantee the safety of fry and help you organize better if you wish to breed them. Female guppies tend to eat their own fry, and if they don’t, your tank will easily get overcrowded. To avoid all that, make sure you check for signs if the female is pregnant. Their abdomen will become bigger, gravid spots will be darker and more visible, and the fish will become calm and isolated. If you see that kind of change, your guppy is pregnant.


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