Do Mollies Eat Their Babies? Tips to Protect Molly Fry

As an aquarist and enthusiast of mollies, I’ve experienced the joy of seeing these adorable livebearers give birth to their fry, but also the worry that follows: Do mollies eat their babies? And if so, how can we protect newborns from their hungry parents?

mollies eat their babies

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Let me share with you the answers I’ve found and some essential tips to ensure the survival and growth of your precious molly fry.

Reasons Mollies Eat Their Babies

As much as it might disturb us to witness our mollies eating their babies, there are specific reasons behind this behavior. Understanding these factors can help us create a safer environment for the fry. Here are the main reasons mollies consume their offspring:

Lack of Parental Instincts

Unlike some other fish species, mollies don’t possess strong parental instincts. They don’t recognize their fry as their offspring, and instead view them as easy prey to satisfy their hunger. It’s an unfortunate reality that stems from their innate behaviors.

Limited Space

In confined spaces, mollies are more likely to come across their fry and see them as a quick snack. If your aquarium lacks hiding spots or is too small, the fry won’t be able to escape from their predatory parents.

Insufficient Diet

Providing a well-balanced diet for your mollies is crucial for their well-being as well as the safety of their fry. When mollies feel hungry or lack essential nutrients, they may resort to eating their babies to fulfill their needs.

Armed with this information, let’s examine some preventative measures to ensure the fry’s survival in your aquarium.

black molly fish

Prevent Mollies from Eating Their Babies

Now that we’ve understood the reasons behind this unsettling behavior, it’s time to implement effective strategies to keep molly babies safe from harm. Here are a few practical tips to prevent mollies from eating their fry:

Separate Tank

The most reliable method for protecting fry is to create a separate tank specifically for them. This allows you to closely monitor their growth, nutrition, and well-being without any fear of predation.

Tank Dividers

If a separate tank isn’t an option, using a tank divider can be an effective solution to keep molly babies away from their parents. Make sure that the divider has small enough gaps to prevent the fry from slipping back into the main tank.

Plenty of Hiding Spots

Provide your fry with numerous hiding areas, like plants (real or artificial), rocks, and other decorations. These safe havens will allow the baby mollies to escape their parents’ attention and grow in peace.

Appropriate Feeding Schedule & Diet

A well-fed adult mollie is less likely to eat its own fry. Regularly provide them with a balanced diet that includes high-quality flakes, pellets, live, and frozen foods. This will help satiate their hunger and deter them from considering their offspring as food sources.

Floating Plants

Mollies usually swim at the middle or top level of the tank, so adding floating plants can offer the fry a safer place to hide. This extra cover can help create a more comfortable environment for your growing babies.

By implementing these measures, you can successfully prevent mollies from eating their babies and give the little ones a fighting chance at a healthy, thriving life.

Black Molly Fish

1. Feeding Adults Regularly

Keeping your adult mollies well-fed plays a crucial role in discouraging them from gobbling up their fry. A robust feeding schedule and a nutritious diet contribute significantly to a healthier, more harmonious environment in your aquarium.

Here’s how you can provide the best nourishment for your adult mollies:

Varied Diet

A balanced and varied diet is crucial for your mollies’ well-being. Their diet should include a mix of high-quality flakes or pellets, live foods like brine shrimp, and frozen foods such as bloodworms. This variety provides the essential nutrients and helps keep them satiated.

Feeding Frequency

To maintain a consistent feeding schedule, feed your adult mollies two to three times a day. Ideally, provide them with the appropriate amount of food that they can consume within five minutes. Overfeeding can lead to water quality issues, so it’s essential to find the right balance.

Feeding Technique

Try distributing the food across the surface of the water, instead of dumping it at a single point. This will engage the mollies in actively searching and foraging for food, minimizing any aggressive behavior.

Monitor Their Diet

Keep an eye on your mollies’ eating habits and adjust the feeding schedule and portions accordingly. Based on their age and size, their dietary needs might change, but prioritizing a healthy, regular feeding routine will help prevent the adults from preying on their fry.

An adequately fed adult molly is less likely to turn to its offspring for nutrition. By ensuring your mollies receive a balanced and ample diet, you create a safer environment for the little ones to grow and thrive.

2. Using a Breeding Box

A breeding box or net is another effective method to protect your molly fry from becoming a snack for adult mollies. Breeding boxes offer a convenient and affordable alternative to setting up a separate tank. Here’s how to use a breeding box for safeguarding your molly fry:

Selection of Breeding Box

Choose a breeding box or net that is large enough to provide ample space for molly fry to swim and grow without any constraints. Ensure the box is made of safe and durable materials that are non-toxic to your fish.


Install the breeding box or net in your main tank, as per the manufacturer’s instructions. Make sure it’s securely attached and won’t topple over or release the fry into the main tank unintentionally.

Transfer of Pregnant Molly

When you notice that the pregnant molly is near the end of her gestation (usually around 30-45 days after mating), transfer her gently into the breeding box. Keep a close eye on her, as the stress of the box can sometimes induce early labor.

Release of Fry

Once the pregnant molly gives birth to her fry, release her back into the main tank, as she can still pose a threat to the little ones. Monitor the offspring closely within the safety of the breeding box or net.

Gradual Transition

Allow the fry to grow within the breeding box until they are large enough to avoid being eaten by adult mollies. Once they’ve reached that size, you can carefully reintroduce them into the main tank.

Breeding boxes provide a practical solution for protecting molly fry without drastically altering your aquarium setup. By giving the fry a safe space to grow, they have a better chance of surviving and flourishing.

mollenesia poecilia sphenops

3. Separating Pregnant Molly Fish

As a precautionary measure, you can separate the pregnant molly from the main tank even before she gives birth, thus reducing the chances of her offspring being eaten. Here’s a step-by-step guide on isolating your pregnant molly fish to ensure the safety of her future fry:

Prepare a Separate Tank

Ideally, set up a second tank specifically for pregnant mollies and their fry. The tank should include hiding spots, plants, and a suitable filtration system. Ensure optimum water quality, as molly fry are sensitive to water conditions.

Identify the Pregnant Molly

Keep a close eye on your mollies to identify when one of them is pregnant. Signs include a rounded, swollen belly and changes in behavior or swimming patterns.

Timing the Transfer

Don’t separate the pregnant molly too early in her gestation, as this can cause unnecessary stress. Instead, wait until she exhibits tell-tale signs of nearing the end of her pregnancy, such as “squared-off” belly appearance or seeking hiding spots to give birth.

Gentle Transfer

Once you determine that your molly is getting close to giving birth, gently transfer her to the prepared separate tank. Minimize stress during this process, as distress can lead to complications or early labor.

Post-Birth Care

After the molly gives birth, return her to the main tank, leaving the fry in the separate tank. Monitor the fry closely, providing them with a well-balanced diet to encourage healthy growth.

By separating pregnant molly fish, you can create a more controlled environment for the babies and prevent possible predation from their mother or other adult mollies in the main tank.

molly fish fry

4. Using Live Plants and Hiding Places

One of the simplest and most natural ways to keep your molly fry safe from adult mollies is by providing an environment rich in live plants and hiding places. These protective spaces give the fry a chance to evade predators and grow in peace.

Here’s how to create an ideal environment for your molly fry:

Live Plants

Incorporating live plants into your aquarium offers numerous benefits, including improving water quality and providing natural hiding spots for fry. Some suitable plants for mollies include:

  • Java moss: A dense, versatile plant that can be attached to rocks, driftwood, or left to float, offering excellent coverage for fry.
  • Hornwort: A fast-growing plant that can float or be planted in the substrate, providing an ideal shelter for little ones.
  • Water sprite: With delicate, feathery leaves, this plant offers plenty of hiding spots when rooted, or it can be left to float.

Artificial Plants

If you find maintaining live plants too difficult, artificial plants can be a valid alternative. Choose plants with fine leaves or branches which create many hiding spots for the fry, and ensure they are made of non-toxic materials.

Other Hiding Spots

In addition to plants, include other decorations that create hiding spots for the fry, such as:

  • Rocks: Arrange rocks to form small caves and crevices for the fry to hide in.
  • Driftwood: Pieces of driftwood can provide great resting and hiding spots.
  • PVC pipes or ceramic caves: Commercial or DIY hiding places can also supplement the natural shelters.

Remember that a safer, more comfortable environment for your molly fry increases their chances of survival. By providing an abundance of hiding places, you give these tiny creatures the opportunity to grow and thrive without the constant threat of predation from adult mollies.

best molly fish tank mates

5. Keeping Different Size Mollies Together

Another tactic to minimize the risk of adult mollies eating their fry is to introduce mollies of various sizes in the same aquarium. The presence of other smaller mollies can deter adults from targeting their offspring due to the following reasons:


In a mixed-size environment, the adult mollies have more distractions, which can divert their attention away from the fry. With multiple fish of various sizes swimming around, the adults are less likely to focus solely on finding and consuming their babies.


The fry can mix in and hide more effectively among different-sized mollies in the tank. As they resemble other smaller fish, adult mollies are less likely to single them out from the rest, thus improving their chances of survival.

Conspecific Aggression

When mollies are kept in a mixed-size aquarium, they are more inclined to display conspecific aggression towards each other rather than focusing on the fry. This reduces the likelihood of baby mollies turning into a snack for the adults.

Keep Balance

While including various sizes of mollies in the same tank has its advantages, it’s essential to maintain the balance between the sizes of the fish. Overpopulation or severe size differences can lead to aggressive behavior, stress, health issues, and other problems for your fish.

By carefully combining mollies of different sizes, you can create a diverse, more harmonious environment that promotes the survival of your molly fry. Remember to monitor your aquarium closely and adjust the fish population and aquarium setup as needed to optimize the living conditions for all your mollies.


Mollies eating their babies might be disheartening, but it’s important to understand that it’s a natural behavior influenced by factors such as hunger, stress, and lack of parental instincts.

By using the tips and strategies mentioned in this article—such as setting up separate tanks or breeding boxes, maintaining a regular feeding schedule, creating hiding spots, and incorporating mollies of various sizes in the same tank—you can create a protected environment for molly fry, increasing their chances of survival and growth.

Ultimately, understanding the reasons behind this behavior and implementing precautions will ensure a better, safer, and more harmonious environment for your precious molly fry.

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