Pregnant Molly Fish: Tips On How To Know And Care For Them

Molly fish is one of the most popular freshwater aquarium fish. They’re hardy, colorful, and relatively easy to care for. It’s also worth noting that Mollies are simple to breed. 

If you have both male and female fish in your aquarium, then the molly will naturally spawn often – but not all of those babies grow up! If they live in the same tank, they will be eaten by other fish or even their parents.

You need to know if your female molly is pregnant and when she will give birth so that you can prepare for the arrival of new baby fish!

But sometimes, it can be challenging to understand if a molly is pregnant, as they have a naturally prominent belly. This leaves many facing problems identifying whether or not they’re carrying new lives inside them!

In this blog post, I’ll share some tips on how to tell if a molly is pregnant and what you should do if she is. Stay tuned!

What Are The Signs Of A Pregnant Molly Fish?

Molly fish are unique in the world of aquatic creatures because they give birth to live young, similar to guppies. Unlike most other fish species, mollies have something called “viviparity.” This means that males and females mate with each other and female mollies give birth to live young. 

When a female molly is pregnant, her organs and skin become thicker to protect the developing babies. She also experiences several changes in behavior that can help you detect whether they are pregnant!

There are several ways to identify if your fish is pregnant. Some signs become visible 7-10 days after fertilization, while others appear throughout her pregnancy term, lasting between 20 – 40 days in length!

Continue reading to learn some valuable tips and tricks for recognizing and caring for a pregnant molly fish and her fry.

1. A Swollen And Stretched Out Belly

Your molly’s swollen belly will be the most apparent evidence that she is pregnant. That implies that she seems a little chubbier around the belly region than usual. Moreover, as her pregnancy proceeds, Molly’s appearance will continue to get plumper and rounder.

Swollen & Rounded Belly

However, mollies won’t have a big tummy immediately after fertilization; therefore, this symptom is generally only significant in the latter few weeks of pregnancy.

The more infants she is carrying, the rounder her stomach will get. Mollies often have a rounder body shape; because of the fact that they may carry up to 120 of them at once!

To ensure that she gives birth in peace and that her babies are protected from danger, you must place her in a separate tank.

2. A Gravid Spot Under Their Belly

The emergence of a blackish mark or line flowing down towards their anal cavity is another easy method to know whether your mollies are pregnant. The black mark is nothing but the young fry’s eyeballs, which can be seen more clearly under UV light.

Gravid Spot

Because the eyes are the most significant part of the fry’s body, this gravid area gets increasingly evident as the fry develops. However, if you have black mollies, the dark mark will not be noticeable. The lighter your molly fish is, the simpler it is to notice. Therefore, you must keep an eye on their abdomen with black mollies.

3. Aggressive And Isolated Behavior

While pregnant, Mollie’s behavior changes, and they become more protective of themselves while also being more hostile towards others. It is nothing more than an inbuilt protection mechanism; yet, the aggression is neither hazardous nor damaging.

Aggressive & isolated behavior

But, more than battling, a pregnant molly will often hide away in the presence of other fish to feel comfortable and avoid being harassed by them.

As early as seven days after conception, this is one of the signs to look for! As a result, to keep a molly fish happy, you need to provide lots of hiding places in the tank.

4. A Pregnant Molly Fish Will Eat More

A pregnant molly fish will consume extra food in order to give essential nutrients for the growth of her fry and herself. When she becomes pregnant, her appetite changes dramatically. 

Eat More

And you may notice her being more active throughout feeding time or even competing for food with her tank mates. Therefore, provide sufficient to ensure that there is enough food for everyone.

5. They Seek Warmth

When mollies get pregnant, they need greater warmth than at any other time. This is because they will so often gather around the heating element of your tank to get warmth.

Seek Warmth

Mollies may also spend more time towards the top of the water if you utilize an overhead UV lamp since the added warmth given by the light source encourages them to do so.

It is your responsibility to maintain a consistent and steady temperature throughout the tank in order to provide the best possible environment for Molly.

How Long Is The Pregnancy Of Molly Fish?

The average gestation period of molly fish is 20-40 days. However, this largely varies depending on the species type you have. For example, a molly fish variety named Dalmatian Molly can stay pregnant for 70 days. 

The molly fish is a very special creature with some truly unique features. For example, they can keep the male’s sperm inside their body for months at a time.

This means they could actually be pregnant consistently over longer periods! They usually fertilize their eggs every 30 days.

How Long Is The Pregnancy Of Molly Fish

Mollies offer exciting moments for aquarium owners as you watch your pregnant molly give birth! However, whether a pregnant molly will give birth depends on the aquatic environment and how comfortable she is. 

They need a warm and comfortable environment with plenty of hiding spots so their babies can be born without any stress! However, many breeders also separate pregnant molly in another tank to ensure they give birth in peace. 

What Are The Pregnant Molly Fish Stages?

Once Molly’s eggs have been fertilized, she goes through a series of phases that correspond to the stages of pregnancy. First, she will experience a hormone surge, which marks the beginning of this journey. 

Here I’ve listed the various stages of pregnant molly fish so that you have a clear idea of how long she has before she may give birth!

Stage 1: Conception

As long as the tank has both male and female mollies, they may get together to breed. A single mating between them can lead to the fertilization of eggs every 30 days!  

Pregnancy Stages of Molly Fish

Stage 2: The Formation Of The Embryo

When an egg is fertilized, a tiny embryo begins forming within each of the sperm’s cells. You can see this happening with your own eyes (appearance of gravid spot) as it starts to form at around 7 days after conception!

Stage 3: The Fry Develop

As your pregnant molly grows, you will notice that her belly starts to inflate. This is because she has begun filling up with fry!

Stage 4: The Pre-Birthing Stage

Fries are getting ready to make their grand entrance into the world. They almost reach the end of their time in their mother’s belly. You can see their eyes more clearly at this stage. But don’t worry – still some more time remaining before popping out!

Stage 5: Birthing Molly Fries

The molly releases her fry, who will have already learned to swim. The birth rate for these fries can reach up to 120 at one time. Unfortunately, it is in this molly’s nature to consume their offspring soon after birth, which is sad!

How To Take Care Of Pregnant Molly Fish

Pregnant molly fish don’t need a lot of attention while they are pregnant. Because of that, breeding molly fish is relatively easy to breed. However, there are several things you can do, though, to help your pregnant Molly feel more comfortable throughout her pregnancy. Keep in mind that a stressed-out fish could abort fries!

  • Provide your molly with some extra shelters or hideouts. They’re always looking for darker, quieter places to avoid conflict during pregnancy with the others in their tank! The more you have of these types around—the better they will feel. 
  • Pregnant mollies can benefit from a warmer temperature. The ideal temperature for molly fish is 72-78 degrees Fahrenheit. A couple of degrees higher will make them feel more comfortable and relaxed during the stressful times of pregnancy! Therefore the tank temperature you should maintain is between 74-80 o. 

How Do I Know When My Molly Will Give Birth?

Predicting when your molly fish will start releasing young mollies may be tricky. However, knowing when your molly is ready to give birth is essential to provide her with the greatest possible environment. 

Here are the most important indications to watch out for to prepare the pregnant molly mother for delivery.

The Gravid Spot Is Very Visible

When your molly is about to give birth, the dark spot under molly’s belly will now be at its most visible point. It has a triangular shape and gets darker as she gets closer to giving birth. Her belly also gets squared off as she approaches giving birth.

As the embryos develop further, you will be able to distinguish the individual fry by their eyes as they become more prominent. Soon after the fry’s eyes become the most noticeable, the mother molly will give birth to her offspring. 

Mollies Will Try To Hide In The Tank

Pregnant molly fish will become more solitary and seek darker places in the tank. She will not want to be bothered by the presence of other fish in her aquarium.

To help her get through this difficult time without any distractions or worries about other tank inhabitants bothering them, provide plenty of hiding spots like plants and shells around the aquarium. 

You can also isolate your pregnant molly fish from the rest of the adult fish. This will assist you in better managing the fry and protecting them from being eaten by other adult fish.

They Don’t Eat & Become Sluggish

Molly fish exhibits a lack of appetite in the latter stages of her pregnancy. During feeding, she becomes lethargic or often refuses to eat altogether. If you detect any of these signs, she is likely going to release her fries.

A Rounded Area Develops Under Their Gills

Besides their bellies, the pregnant molly fish will begin to fill out in other regions as well, particularly underneath their gills. This indicates that her womb has reached its maximum capacity and that she is on the verge of giving birth. She will make every effort to give birth as soon as possible in order to relieve the stress!

How to Save Molly Fry

It’s tragic that these little fries need to be saved from being eaten by their own parent! You need some preparation and arrangements to do that before your pregnant molly gives birth. Let’s explore the ways you can save your molly fries. 

Separate tank

The best way to keep fry safe from adults is by moving pregnant molly into a separate tank or breeding box. 

However, shifting to a separate tank is the most effective option. It allows the fries more freedom, and you can also give special attention to them. In addition, you can create an ideal place for fry to survive by regulating the tank temperature and other parameters to an optimum point. 

For that, you need to prepare the tank with the necessary equipment in advance. First, you must use an aquarium filter. Don’t let them get sucked into the intake. Put something like foam or sponges over filter suction so those delicate animals can’t be pulled inside.

Fry needs a heater in their tank so they can keep warm. The temperature should range from 72-78 °F (22 -26 °C), which is the natural habitat’s water reference point for these little guys! So you need a small aquarium heater to maintain the tank temperature at that range. 

You should use the main tank water for the separate tank to ensure your pregnant molly doesn’t feel stressed after being shifted. As soon as she gives birth, it is essential to put her back in the main tank. And in your separate tank, you’ll only raise the fry. 

Breeding Box

On the other hand, if you want to use a breeding box, the aquarium water must be in its best condition with no ammonia or nitrites. You also need enough hiding space for your fish. 

Separate the pregnant Molly fish from others by shifting her in the breeding box until she gives birth. When she gives birth, the fry will fall into an empty section of the breeding box, leaving the mother molly alone!

Having Lots of Live Plants

If you want to give your molly’s fry the best chance at survival, it is crucial that they live in a tank with lots of plants and hiding places. Young fry need places to hide before they are born.

Therefore, you should add plants, decors, rocks, caves, etc., to offer hiding spots before pregnant Molly gives birth. 

Fry, the little ones often take shelter in floating plants right after birth to avoid being eaten by their own kind or other predators!

So make sure you have at least two to three types of floating plants in the separate tank, breeding box, or main aquarium. Some of the best plants for molly fish are duckweed, hornwort, java moss, etc. 

This way strongest fries will be alive by hiding themselves in these plants and decors until they grow bigger. Then, in about 2 weeks, they will grow enough to not be eaten by other fish! 

Frequently Asked Questions (FAQ)

How Do You Know if Your Fish Is Bloated or Pregnant?

Your fish may get rounder as a result of overeating. However, if you suspect she is pregnant, there will be a gravid spot under her belly where the eggs develop into fry! 

What to Feed Baby Molly Fish?

Molly fry needs a diet similar to what an adult mollie eats, just in smaller pieces. Some excellent food for the little mollies includes brine shrimp, flake, or pellet foods with blood worms and daphnia, all chopped up into very tiny bits of goodness!

How Many Babies Do Mollies Have?

Mollies are known for their large families! Some molly owners report having up to 120 babies in one litter. This heavily depends on the type of fish you have, but most will lay between 20-100 fry per breeding session (or birth).

Do Molly fish protect their babies?

No, not at all. Livebearing fish like mollies are great breeders, but their babies get no protection. The tiny fry can easily be eaten by its mother or other inhabitants of an aquarium, so they need some help!

What can mollies breed with?

In the world of fish, many different species can intermingle to create new breeds. For example, Molly fish can breed with guppies. The case with these two particular types is fascinating because they belong mainly to one genus – Poecilia!

Do Mollies give birth at night? 

Yes, most mollies indeed give birth at night. This helps ensure their fry has the best chance of survival in a tank with others like them! However, there have been reports of mollies giving birth during the day in rare instances.

Wrapping Up

That’s all for now, fish fans. I hope you’ve learned how to detect and care for pregnant molly fish.

If you suspect your molly fish might be pregnant, there are several signs to watch out for. The most obvious is a swollen belly and a gravid spot (larger than usual). We’ve also listed some behaviors that may indicate pregnancy!

If you have anything more to know or want to leave your own tips on breeding mollies, please feel free to do so in the comments below.

Sujit Modak

Leave a Comment