How Long Is A Guppy Pregnant? (Gestation Period Explained)

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I remember how excited I got the first time I raised a pregnant guppy fish. Its belly got swollen, and it presented all the typical signs of a pregnant guppy fish. But I wasn’t sure how long it would take before the fish was ready to give birth. Luckily, as time passed, I gained some experience in this field.

Guppies are typically pregnant for 21 to 31 days. As a rule of thumb, guppies are pregnant for shorter periods if the aquarium conditions are suitable, including the temperature, pH, and hardness. Some guppies will give birth faster due to high temperatures, but that may result in a deformed fry.

As we move forward, I will elaborate on the gestation period of a pregnant guppy fish. I will also mention how you may hasten this period and whether you should. Then, I will show you how to adjust the water parameters so that your guppy gives birth on time.

Still curious? Feel free to check my complete guide on pregnant guppy fish. There, I discussed how to care for pregnant guppies, how long they remain pregnant, how to identify signs of pregnancy, and a lot more.

How Long Is A Guppy Pregnant For?

Guppies are livebearers. Once the male guppy inseminates the female, the female fish will give birth to live babies several weeks down the line. 

Some people use signs such as the color of the gravid spot to estimate the due date of a pregnant guppy. This gives them an idea of when they should move the guppy to a separate tank.

Others base their decisions on the average gestation period of guppies. But you have to apply caution when calculating the gestation period of a guppy because it may vary from fish to fish.

Generally, guppies have a gestation period of 21 to 31 days. However, some pregnancies last an average of 22 to 26 days. You will know that the guppies are about to give birth because they will develop a square bulge below the gills. 

They will also spend more time hiding and start rubbing against objects. It takes these creatures two to six hours to give birth, and they can produce 50 to 80 babies within this period.[1] In extreme cases, the guppy can take up to 12 hours to push all the fry out. 

Bear in mind that guppies usually start getting fat after two weeks of conception. Therefore, if your guppy’s belly is already swollen, it will probably give birth within one to two weeks. And if the belly is already angular, the fish will deliver the fry within the next few days.

Some guppies won’t give birth at all. It is common practice to move the females to separate tanks to prevent them from giving birth in the presence of predators that may eat the babies.

However, the mother cannot remain isolated in the breeding tank for extended periods. If it fails to give birth within 24 hours, you should move it back to the main tank.[2] At that point, you should continue counting down. The gestation period is not over. For whatever reason, the guppy has extended its pregnancy.

Some aquarists forget to resume the count. They don’t realize that a guppy that has failed to give birth despite manifesting all the signs of labor could extend its pregnancy by several days, if not weeks.

Can You Make Guppies Give Birth Faster?

Believe it or not, the conditions in a tank can either delay or speed up a guppy’s gestation period. Under the right circumstances, a pregnant fish can give birth within 21 days. First of all, you have to maintain the appropriate conditions in the aquarium to prevent the guppy from aborting its babies. 

These are the ideal water conditions for pregnant guppies:

  • Temperature: 77-79° F (25-26° C)
  • pH: 7-7.6
  • Hardness: 7-12dGH
  • Ammonia & nitrites: 0 ppm
  • Nitrates: <20 ppm

I also suggest creating a regular day/night cycle (8 – 12 hours of daylight and the same duration of nighttime). Also, the tank requires regular water changes (25 percent each week). These steps will ensure that the guppies give birth within the 22 to 26-day period. 

If you want the creatures to give birth early, raise the temperature. But bear in mind that fish hate instability. Raising the temperature suddenly by several degrees would achieve the opposite result. 

It would cause the guppies to extend their pregnancy. If you wish to shorten the gestation period, you have to raise the temperature by one or two degrees each day.[3] 

The ideal temperature for successful breeding among guppies is 76 degrees F. But if you raise that figure to 82 degrees F, the guppy could give birth within 21 days. One other option is to feed the fish items like brine shrimp and bloodworms with high protein content. 

However, speeding up the gestation period does not always produce positive results. The guppy could produce fewer babies than usual. It could also deliver deformed fry.

Spotting these deformities is not easy, especially for amateurs. In fact, you may not realize that the babies are deformed until they mature. Experienced aquarists know that premature fry have a yellow sack behind the eyes.

In a healthy fry, that section is silver. Additionally, healthy fry are active, whereas their unhealthy counterparts are lethargic. They may die within days of being born. You could extend their lifespan by feeding them high-quality food and keeping their tank clean. But there is no point in rearing deformed fry.

The right conditions will speed up the gestation period. The wrong conditions will produce the opposite result. Extreme temperatures, fluctuating pH, and stress can prevent a guppy from giving birth on time. 

Some guppies will extend their gestation period. Others will refuse to give birth. They will reabsorb their offspring or abort the babies.

To monitor the pH, ammonia, nitrates, and nitrites, I personally use the API Water Test Kit (link to Amazon). After testing dozens of kits, this is probably the most accurate. Within five minutes, you’ll know if something is wrong with the water.

I also suggest considering a water conditioner, such as the well-known Seachem Prime (link to Amazon). Besides fixing abnormalities in the water, this product also prevents toxins from spiking in the future.

Generally, if the water isn’t suitable for pregnant guppies, adding a water conditioner is better than conducting a drastic water change. This will cause less stress in your guppy and ensure that the fish doesn’t abort its fry.

How Fast Can Guppies Get Pregnant Again?

Female guppies can store sperm to fertilize their eggs without the direct involvement of a male fish. Unlike humans, guppies do not require much in the way of downtime in between pregnancies.

A female guppy can conceive mere hours after giving birth. If this is news to an aquarist, their estimate for the guppy’s gestation period may be off by one or two weeks, especially if they believe that the guppy requires a few days or weeks of rest before it can get pregnant again.

Do All Fat Guppies Give Birth At Some Point?

Some people start estimating the guppy’s due date the moment they notice the bloating. However, you need to realize that guppies can swell for other reasons besides pregnancy. 

For instance, constipation can cause a fish’s stomach to distend.[4] But a constipated fish will only swell to a certain point. If you treat it, the fish will shrink. A pregnant guppy will continue to swell. 

Also, if the creature has a disease, you will observe additional symptoms. For instance, if the fish has dropsy, it will develop pinecone scales.

At What Age Do Guppies Start Breeding?

You don’t have to force guppies to breed. If you have a male and female fish in the same tank, you can expect them to mate within a few days. However, like every other animal, guppies must first attain sexual maturity before they can breed.

Guppies are sexually active at six weeks. But it usually takes an average of five months for the creatures to start breeding. If your guppies are sexually mature and they have been in the same tank for several days, you can confidently assume that the female is pregnant. 

You can start counting down the days, especially if the female has begun manifesting the common signs of pregnancy, including a darkening gravid spot and bloating.[5]

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Pro tip: If your guppy is pregnant and will give birth soon, you’ll need to know a little more about the babies. On that matter, feel free to check my complete guide on guppy fry.


Guppies are very easy to breed. In fact, you don’t need to force them to mate. If you have a male and female guppy, they will breed in a matter of days. But the gestation period for female guppies can vary widely. 

Some pregnant fish will give birth within 21 days. However, others could prolong it to 31 days or more. The length of the gestation period depends on many factors, including temperature and water quality. To ensure that your guppy gives birth in time, create a stable environment with minimum stress. 

It is also worth mentioning that it takes time until young guppies reach sexual maturity. While they can potentially reproduce within a few weeks, most guppies only breed at the age of five months. On the other hand, it doesn’t take long between pregnancies. Sometimes it is a matter of days or hours.