Should I Separate Pregnant Guppies? (Pros And Cons)

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Realizing that your guppy is pregnant can be exciting. But it also involves numerous questions. For example, many aquarists are unsure whether they should separate the pregnant guppy from other fish. I even asked this myself when I started this hobby. Luckily, over the years, I gained some experience in this field.

Aquarists should separate pregnant guppies. That will prevent other fish from harassing the vulnerable guppy and potentially cause a miscarriage. However, the tankmates should be separated from the pregnant guppy, not the other way around. Moving the mother will cause unnecessary stress.

As we move forward, I will show you the pros and cons of separating pregnant guppies from other fish. Then, I’ll discuss separating the pregnant fish from the fry without causing stress. I will also list the water parameters you should aim for with pregnant guppies.

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.

Should I Separate Pregnant Guppies?

Well, it depends. Some people expect pregnant guppies to give birth in separate tanks or breeder boxes. They do not want the fish to spend their gestation period in a community tank, surrounded by other creatures.

However, aquarists are not obligated to separate pregnant guppies. They can do whatever they want, including keeping the pregnant females in the main tank. 

That being said, people that support the practice of separating pregnant guppies have several good reasons for doing so, including:

1. Guppies Are Likely To Eat Their Fry

The primary objective of separating pregnant guppies is to protect the fry. Fish are dangerous because they are opportunistic feeders. They eat whatever fits in their mouths, regardless of their temperament.

This puts guppy fry in a difficult position because they are 0.6 mm in length when they first emerge.[1] An adult guppy fish will swallow them whole.

To protect them, you have to separate the pregnant mother from her tankmates. And once it gives birth, you should remove the mother. Otherwise, it will eat its offspring. 

Guppies are bad parents. They do not participate in the rearing of their children. More importantly, they are just as likely to eat the fry.

It can take young guppies anywhere between six and eight weeks to grow to a size where they can survive in the main aquarium.[2] At eight weeks, they are too big for adult fish to eat. 

2. It’s Easier To Maintain The Proper Water Parameters

Pregnant guppies in stressful environments can abort their babies or reabsorb them. They may also extend their pregnancy beyond the typical duration. 

Stress in a tank has numerous sources, and the most prominent is poor water conditions. That includes fluctuating pH, extreme temperatures, and a high ammonia concentration. 

A healthy guppy will respond negatively to poor conditions. Pregnant guppies are more sensitive to poor conditions in the aquarium because the pregnancy has already compromised their health.

This is why many aquarists prefer to care for pregnant guppies in separate tanks. Maintaining the appropriate conditions in an aquarium with one fish is so much easier.

You can adjust the parameters to fit the requirements of the female. Pregnant guppies require a temperature of 77 to 79 degrees F, pH of 7.0 to 7.6, and a hardness of 7 – 12 dGH.[3] Also, the nitrates, nitrites, and ammonia should be kept at 0 ppm.

To measure the pH, ammonia, nitrates, and nitrites, I personally use the API Water Test Kit (link to Amazon). That bundle is highly accurate and easy to use. It also lasts for hundreds of measures, making it highly cost-effective.

Community aquariums are more difficult to maintain because you have to accommodate the needs of different species. Additionally, the more fish you have, the more ammonia they produce. 

That is why it is more challenging to keep the water clean in a community tank. But a single pregnant fish in a sizable tank won’t present a challenge. 

3. Your Guppy Won’t Have To Compete Over Food

Pregnant guppies require a nutritious diet. Unfortunately, the creatures become weaker and more lethargic as their pregnancy advances. They don’t have the strength to fight for food. 

Even though their appetite tends to fade over time, they still need food. At the very least, you have to ensure that the food is available if they want it. This is easier to do in a separate tank where the guppy doesn’t have to fight for or chase after food.

4. The Male Guppies Won’t Harass The Female

Guppies are easy to breed because male guppies are pretty enthusiastic about mating. In fact, you have to keep two to three females for every male guppy to prevent the males from harassing the females to death.

The male guppy’s passion is good because it compels the males to inseminate multiple females, increasing the number of fry your female guppies will generate. But that passion can become a problem once the female is pregnant.

Male guppies won’t hesitate to mate with pregnant females, who can hardly handle the pressure. If you don’t want them to abort or reabsorb their offspring, you should move the females to a separate tank.

5. Other Fish Won’t attack Your Pregnant Guppy

Passionate male guppies are not your only concern. Species such as cichlids, angelfish, and Endler’s livebearers are dangerous to guppies.[4] 

Healthy guppies can survive in a tank with these species, especially if they have plenty of hiding places. But pregnant guppies are neither fast nor strong enough. You have to separate the fish to keep them safe, or they may refuse to give birth.

What Are The Disadvantages Of Separating Pregnant Guppies?

As you can see, separation makes sense. Or, at the very least, it has several obvious benefits. So why are some aquarists opposed to the practice? Well, it has some notable disadvantages, including:

1. You Can Easily Stress Your Guppy

Moving pregnant guppies from the main tank will induce stress. Some healthy guppies are occasionally overcome with shock whenever you transport them to a new tank. 

The consequences for a pregnant guppy are worse because the fish is so weak and vulnerable. Some aquarists have seen that it is better to leave the female in the main tank. 

If you give it enough foliage and decorations, it can hide from potential predators long enough to give birth. Once the fry appear, they can also use the plants and decorations to hide from their parents.

2. It Can Be Expensive

Have you ever installed a breeder box? Well, the process requires a lot of time and effort. You must furnish the breeder box with air valves, pumps, tubing, plants, etc.[5] If you want the pregnant guppy to live in a separate tank, you must buy and prepare a separate tank.

Many aquarists are forced to sell or euthanize their fish because their tanks are too crowded, and they can’t afford to buy a new tank to accommodate the excess fish. 

The notion of purchasing a separate tank for a pregnant fish or even installing breeder boxes and dividers won’t appeal to them. The process consumes too much time and resources. It is much easier and cheaper to add more plants to a community aquarium.

3. Breeding Boxes Can Be Stressful For Guppies

Breeder boxes are problematic because they are small. A pregnant livebearer cannot afford to extend its stay in a breeder box because the stress can lead to premature labor. You could lose all the babies. 

Some aquarists put their guppy in a breeder box as soon as it starts showing signs of pregnancy. But this is a mistake. Breeder boxes require precise timing.

You have to place the fish in the box when your guppy is about to give birth. Guppies are generally pregnant for 21 to 31 days. This is why you should only use a breeding box towards the end of the 4th week of pregnancy. 

And once the guppy has done giving birth, you should take it out immediately. However, for many aquarists, breeder boxes are not worth the trouble. 

If they ran the risk of losing some or all the babies because of the premature labor induced by the breeder box, they might as well keep the pregnant fish in the community tank.

What Is The Verdict?

It is best to separate the pregnant guppy but not remove it from the tank. Instead, it is better to remove the tankmates while leaving the female in the original tank. You should also remove the male mollies. Otherwise, they will keep chasing down the female.

Once the female is alone in the tank, consider adding some foliage. That will allow the newborns to hide once they pop out. You may also install an aquarium divider. This way, the tiny fry will escape to the other side of the tank.

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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.


Pregnant guppies are incredibly vulnerable, which is why you should separate them from other fish, including the males. But instead of taking out the mother, you should remove her tankmates. That will cause less stress and remove breeding boxes from the equation.

Then, I suggest that you add as many plants and decorations as possible. That will keep the female from eating her fry once they are born. You can also use a divider with tiny holes. That will allow the fry to escape to the other side of the tank.

Don’t forget to test the water parameters. Ensure that the pH, temperature, ammonia, nitrates, and nitrites are within the desired range. If they are not, conduct small and gradual water changes.