How To Tell If A Guppy Is Pregnant? (Signs & Behavior)

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The first time I saw my female guppy fish becoming swollen, I wasn’t sure if it was pregnant or sick. Obviously, the most apparent reason is that the fish is indeed pregnant. However, I’ve heard that some guppies may become fat due to constipation. As time passed, I learned that there are actually many signs suggesting that a guppy is pregnant.

These signs indicate that a guppy fish is pregnant:

  1. The belly will gradually swell day by day.
  2. The gravid spot turns darker.
  3. The guppy will spend most of its time hiding.
  4. The fish will become aggressive towards its tankmates.
  5. Pregnant guppies are less interested in food.
  6. The fry eyes might be seen at the lower part of the abdomen.
  7. The guppy will lose its colors and become pale.
  8. Your guppy will swim at the top sections of the tank.

As we move forward, I will share some valuable pictures that illustrate the signs of a pregnant guppy fish. I’ll also include a helpful Youtube video demonstrating pregnant guppies’ behavior.

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 To Tell If A Guppy Fish Is Pregnant?

Guppies breed easily and quickly in captivity. Once a male and female guppy is in the same tank, the male fish will fertilize the eggs inside the female fish’s body. Thirty days later, the mother will produce living babies.[1]

During the guppy’s gestation period, you should watch for the following signs. They prove definitively that the guppy is pregnant:

1. The Guppy’s Abdomen Will Gradually Swell

Pregnant livebearers have bulging stomachs. Male and female guppies have different body shapes. While the males are long and slender, the females are large and round.[2] However, a pregnant female’s belly will swell beyond the usual parameters. 

It should be noted that a guppy’s stomach can swell for other reasons besides pregnancy. This is where many aquarists stumble. They will confuse digestive complications like constipation for pregnancy.[3] 

Fortunately, a swollen belly is just one symptom among many that signify pregnancy. It is also worth noting that a pregnant guppy’s belly will continue to expand throughout its gestation period, which may last between 21 to 31 days.

If the fish is swollen because it ate a lot of food, the belly will shrink in the next few hours as the creature digests the food. Constipation is the same. If you treat the ailment, the guppy’s stomach will shrink. 

But if the fish is pregnant, the belly will get bigger and bigger. When the guppy is close to giving birth, the creature’s body will take on an angular shape.[4]

2. The Gravid Spot Becomes Darker

The gravid spot is one of the most definitive signs of pregnancy in livebearers like guppies. The gravid spot is a dark mark near the anal vent. People think that the gravid spot appears during pregnancy and disappears when the female gives birth. But that is not true.

Every female guppy has a gravid spot. In fact, you can use the mark to identify the guppy’s gender.[5] When the fish is pregnant, the gravid spot grows dark, making the mark easier to see.

Some guppies have a red, orange, or brown gravid spot. But as the pregnancy progresses, the mark will get darker and darker until it is black.

3. Your Guppy Will Keep Hiding

Pregnant guppies are listless. They don’t spend as much time swimming as they did before they fell pregnant. Some females will become secretive. They will find a comfortable object or plant behind which they can hide.[6]

The objective is to find a safe place to give birth privately, away from potential predators. Also, pregnant fish are weak and vulnerable. They do not want to expose themselves or their offspring to bullies that may attack them.

For this reason, some pregnant guppies may disappear altogether. You won’t see them for several days, possibly even weeks. This isn’t a problem if your guppies are healthy and the conditions in the tank are appropriate.

This behavior only presents a challenge when the pregnant guppy dies in hiding because of complications related to childbirth. It may decompose before you can find and remove it.  

4. Your Guppy Will Become Aggressive

People associate pregnancy among livebearers with timidity, and for a good reason. Pregnant females spend a lot of time hiding. But that doesn’t apply to every single guppy.

Some expectant mothers will manifest an aggressive streak because their instincts push them to protect their unborn offspring. They will lash out at any fish they perceive as a threat.

In the best-case scenario, the females will chase away any fish encroaching upon their breeding ground. In the worst-case scenario, your female’s actions may spark a bout of violence among the guppies, creating an unsafe environment for the pregnant fish.

Guppies are fascinating creatures because they don’t have to give birth if they don’t want to. A pregnant guppy will either reabsorb its eggs or abort the offspring if it doesn’t feel safe in the aquarium.[7]

This is why some aquarists prefer to separate pregnant guppies. They don’t want the other fish to oppress the females when they are sensitive and vulnerable.

5. The Guppy Will Be Less Interested In Food

Pregnant guppies have an aversion to food. They may eat more than usual in the initial stages of the gestation period. But over time, their appetite will wane until they lose all interest in food.[8]

This is not an excuse to stop feeding the guppies. They still require food but in smaller amounts. Because their appetite has faded, the volume of leftovers in the tank will increase, especially if the pregnant female lives alone.

By reducing the quantity of food, you can also reduce the amount of cleaning you have to do. Ultimately, you have to make sure the food is available just in case the pregnant female decides to eat. Some fish will eat the food and then spit it out later on.[9]

6. The Fry Eyes Will Apear In The Gravid Spot Area

If the gravid spot on your guppy has always been prominent, and you can’t tell whether or not it has grown darker, look for the eyes of the babies. At a distance, they look like tiny black dots.[10]

Fish have relatively translucent bodies. This is why some fish develop new patches of color when they eat certain foods. You can see the food as it moves through their bodies. As such, when the eggs in their wombs hatch into fry, you can also see their eyes through the guppy’s skin. 

This is the most definitive sign of pregnancy in this species. As the creature approaches its due date, one additional symptom to look for is body contractions. This is where the muscles along the guppy’s body tighten and relax.[11]

7. Your Guppy Will Lose Its Colors

Pregnant guppies may lose their color. Sometimes, this is restricted to the gravid spot, which may become lighter instead of darkening. On other occasions, the guppy’s entire body will become discolored. 

Unfortunately, guppies can lose their colors for various reasons, including stress, disease, poor water conditions, and a lousy diet. Don’t assume that your guppy is discolored because it fell pregnant until you observe all the other signs. 

You should also realize that pregnant fish are just as susceptible to diseases as their non-pregnant counterparts. In other words, a pregnant guppy may lose its color because it is sick.

Don’t limit your search to the various signs of pregnancy. You should also look for signs that may point to the presence of an illness, including white dots, ripped fins, heaving breathing, lethargy, etc.

If you still feel uncertain, here is an excellent Youtube video that illustrates the signs and behavior of a pregnant guppy fish:

8. The Guppy Will Swim At The Top

This is actually a sign that your pregnant guppy is about to give birth. Pregnant guppies will frequent the upper sections when they are close to their due date. Guppies prefer to swim in those areas because they are oxygen-riched.

By spawning in an environment with high oxygen levels, pregnant guppy fish ensure that their fry will find it easy to breathe once they are born. That also helps the mother herself, as the spawning process is stressful and requires a significant amount of energy.

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.


If you suspect that your guppy is pregnant, first determine whether the fish is a male or a female. Luckily, female guppies are easy to identify, as they are relatively big and pale. They don’t share the intense colors male guppies have.

Then, look for signs of pregnancy. That includes a belly getting larger and larger, a loss of appetite, and a darkening gravid spot. If your guppy got fat, but then the abdomen shrunk a little, it is probably not pregnant. Constipation may explain this change.

Also, pregnant guppies spend a lot of their time hiding. As they are incredibly vulnerable at this stage, they will do everything to avoid predators. That is a survival instinct almost all guppies share.