How Do You Know When A Guppy Is Going To Give Birth?

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One of the most frequently asked questions about pregnant guppies is when they will give birth. That was the first question I had when I realized my guppy was pregnant. Luckily, over the years, I learned how to tell if your guppy is in labor and prepare the tank accordingly.

These signs indicate that a pregnant guppy is going to give birth:

  1. You will notice contractions across the guppy’s body.
  2. The guppy’s belly will appear boxy.
  3. Your guppy will hide and start breathing heavily.
  4. The gravid spot will darken.
  5. The fry eyes will be seen at the lower part of the abdomen.
  6. The guppy will have no interest in food.
  7. Your guppy will lash out at other fish.
  8. The guppy will reach the 4th week of its pregnancy.

As we move forward, I will share some pictures that will help you identify a guppy fish about to give birth. Then, I will share my thoughts on what you should do once you notice these signs. This will help you prevent the parents from eating their newborns.

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 Do You Know When A Guppy Is Going To Give Birth?

You don’t have to force your guppies to mate. The creatures are enthusiastic breeders. If you know what to expect from healthy guppies, it won’t take you long to identify their pregnant counterparts.

This is especially true for guppies on the verge of giving birth. They tend to manifest unmistakable signs, including the following:

1. You Will Start Noticing Contractions

Look for contractions. The muscles on the surface of a pregnant guppy’s body will tighten and loosen rhythmically.[1] This tells you that labor has begun or it’s about to start. It is not uncommon for fish to rub their bodies against objects in the vicinity. 

A guppy can give birth to two babies. This is normal. However, aquarists expect their fish to produce dozens of fry, possibly even hundreds. 

Don’t be so quick to assume that the birthing process is over when you’ve only seen two or three fry in the water. Give the fish a few more hours. It may push more babies out. 

2. The Belly Will Grow Boxy

The female guppy will swell as its pregnancy progresses. Unlike regular bloating caused by ailments like constipation, the fish will continue to grow in size until it looks like it’s on the verge of bursting.

Eventually, the fish will become boxy.[2] The expansion of the guppy’s belly is part of the reason why the gravid spot distends over time.

3. Your Guppy Will Hide And Breathe Heavily

In some cases, when the gravid spot becomes black or maroon, the guppy will start breathing rapidly.[3] In most situations, this is a sign of illness and stress. But here, the guppy is merely approaching its due date.

In preparation for the emergence of its babies, the creature will also hide. Because the fish is weak and listless during this period, it doesn’t want to give birth out in the open where predators may take the opportunity to attack it.

As such, the female will search for a secluded area to give birth in peace. If the tank has dense foliage, the guppy may remain out of sight entirely until it gives birth.

If you haven’t separated the female from its tankmates in the community aquarium, but you want to protect the babies from predators, observe the tank carefully and scoop out any fry you see.

The offspring can survive for a while in an environment with dense foliage. Therefore, don’t panic if you can’t get to all the babies the moment they emerge from the female’s body.

4. The Gravid Spot Will Turn Intensely Black

The gravid spot is the dark patch near the anal fin. You can use the gravid spot to identify the womb. This mark will grow in size as the eggs hatch and the babies develop. It will also darken, a typical sign that the guppy is pregnant.

Scientists can use the transformation the gravid spot undergoes to predict the development of the babies inside a livebearer.[4]

This is true for aquarists as well, mainly if they have reared many guppies in the past. The gravid spot is at its darkest and most prominent when the guppy is close to giving birth.

5. You May See The Fry Eyes

Disturbing as it might sound to newcomers, you can see the eyes of the babies through the belly of a guppy that is about to give birth. The gravid spot is typically black by this stage. 

However, you can see the eyes of the fry through the gravid spot because the female’s body has expanded, making the babies easier to see through the thin walls.[5]

6. The Guppy Will Lose Its Appetite

Female guppies become less active as their due date approaches. Eventually, they will find a safe location and sit or hover. They tend to favor areas near the heater. You can also look for them in the corners and behind plants and decorations.[6] 

At this point, they don’t have much of an appetite. They will ignore the food you add to the tank. You see these symptoms in stressed fish. They will lie still at the bottom, showing little or no interest in food.

Pregnancy is stressful. Therefore, don’t be surprised if you start observing conventional signs of stress. The fish will start eating once it gives birth. Though, you should add food to the tank just in case the creature gets hungry before it gives birth.

7. Your Guppy Will Become Aggressive

If your fish is hiding because its due date is fast approaching, it will manifest signs of anxiety or aggression whenever you approach its hiding spot. Pregnant guppies hide because they want privacy and security. 

They may lash out at any creature that approaches them during this period, especially if the fish in question is a male guppy that wants to mate with the female.[7]

8. It Will Be The End Of The Gestation Period 

People want to know when a guppy will give birth because it helps them prepare accordingly. They have to move the pregnant fish to the breeding tank to protect the fry.

But amateur aquarists do not have the experience required to identify the signs of imminent labor, which is why some of them prefer to estimate the guppy’s due date using the average gestation period.

Guppies are typically pregnant for 21 to 31 days. Using this information, you can estimate the creature’s due date. Though, this method is unreliable because the gestation period of a guppy can vary widely depending on conditions like the temperature.

Some guppies can give birth within 21 days. For others, the pregnancy may last 40 or more days. In some cases, your guppy will not give birth at all.

You can still base your decisions and preparations on the average gestation period. But if your goal is to move the guppy shortly before it gives birth, you have to observe the aquarium closely after the first 20 days because the babies can pop out at any moment.

It is easier to make an accurate estimate of a guppy’s due date if you regularly observe the aquarium. You are more likely to notice signs of mating. Mating guppies will chase each other around the tank for a while because the male fish finally injects its sperm into the female fish. 

If you saw the guppies mating, you can start the countdown. If the female fish used stored sperm to fertilize its eggs, you have no way of knowing when conception occurred.

What Should I Do If My Guppy Is About To Give Birth?

If you suspect that your guppy is about to give birth, the first step would be installing an aquarium divider. Since the guppy parents are likely to eat their fry, it is best to create some sort of separation.

You may also consider a fry trap. The idea is to trap the fry as soon as they are born, so bigger fish cannot chase them down. Here is an excellent Youtube video that shows how to do that, using a simple plastic bottle:

Once the fry are trapped, and the female guppy has done giving birth, you may move her to a different tank. I also suggest removing any other fish that can potentially eat the fry. It is best to use the same water from the original tank when starting a new one.

Then, I suggest adjusting the water parameters for the newborns. These are the parameters you should aim for:

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

To measure the pH, ammonia, nitrates, and nitrites, I personally use the API Water Test Kit (link to Amazon). This kit is highly accurate. It also lasts for eight hundred measures, making it highly cost-effective.

If you found this article helpful, these may also interest you:

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.


You can tell that your guppy is going to give birth if it starts manifesting specific signs, including a dark gravid spot, a decrease in appetite, and an aggressive attitude. You can also tell that it is about to give birth if you see the fry eyes.

Once you notice these signs, you might want to create a physical barrier to protect the babies. Or, you might decide to use a fry trap to catch them as soon as they are born. Then, once the fry are safe and sound, you can move the female guppy elsewhere.