Pregnant Molly Guide: Signs Of Pregnancy And Overall Care - Badman's Tropical Fish (2024)

First-time breeders can have quite a few questions about a pregnant Molly.

Generally, there’s a lot of confusion among fish keepers about Molly’s pregnancies. Presumably, that’s because there are so many varieties of the species out there.

Before you get too anxious about the care and maintenance of your pregnant Poecilia Sphenops, relax. A Molly gestation will function the same way, no matter the variety you have.

Plus, you now have the option of referring to our thorough Molly pregnancy guide that covers all you need to know about breeding the species successfully!

How To Tell if a Molly Is Pregnant

If you’re curious to learn the signs of pregnancies in Mollies, chances are you’ve noticed something different about your fish. More often than not, aquarists notice their fish getting thicker around the tummy area.

However, there are quite a few other ways to make sure your Molly fish is pregnant, so you can start prepping for the arrival of little ones. Read below to know if you have your female Molly fish pregnant:

• Swollen Belly

As stated earlier, Mollies can give birth to around 100 to 120 fry in one go. Plus, there’s no such thing as Molly eggs because the species are livebearers.

Naturally, when a fish that reaches up to four and a half inches in length (upon maturity) carries around 100 tiny fry, it’s going to show.

That’s why one of the most noticeable signs of pregnancy for this species is the female going rounder around the belly area as the pregnancy progresses.

However, just the presence of a growing belly isn’t enough to be sure your Molly is expecting. Aquarists should also look out for other signs listed below:

• Behavioral Changes

Thankfully for fish keepers, identifying a gestation among the species is easier because of pregnant Molly behavior.

Once the fish has conceived, you’ll notice your generally peaceful and well-behaved Molly turn somewhat aggressive.

However, this doesn’t mean you can expect to see your female Molly attacking others without reason.

Instead, a pregnant Molly will not take kindly to other fish that disturb its rest in any way. That’s generally why pregnant Mollies prefer spending most of their time in convenient hiding spots during the pregnancy.

• Increased Proximity to Water Heater

Another curious sign of a Molly pregnancy is that the female will take to staying closer to the aquarium’s water heating system.

It’s not entirely clear why female Mollies like doing this. Still, professional aquarists state this has to do with the pregnant Molly trying to maintain a stable temperature throughout the gestation.

If your lighting setup includes UV lights, you may also notice your Molly fish swimming close to the water’s surface. Since UV lights emit heat, they’re another convenient way to keep pregnant Mollies warm.

• Gravid Spot

Fish experts will tell you that all livebearing fish species sport a gravid patch near their anal fin. This spot generally grows a little in size and changes color during the fish’s gestation period.

Similarly, you can confirm your Molly fish is expecting when you notice the gravid spot around its lower body darkening in color. If you’re wondering what causes the spot to change color, that’s simple.

The gravid patch is located near where the Molly fish carries the fry inside its body. As the fry grow and develop, their eyes become the largest part of their bodies.

Since Molly fish have translucent skin, you can see the changes occurring inside its body through the Gravid patch.

How Long Are Mollies Pregnant?

A Molly pregnancy can last from 20 to 40 days, and birthing can occur towards the end of this period or immediately after.

Molly fish achieve reproductive age when they’re pretty young. Male mollies reach sexual maturity at about 12 months of age, whereas female Mollies can breed when they’re six months.

That means if you’re not planning to breed Mollies and add to their numbers, you may want to keep males and females separate until you’re ready to let them reproduce.

Once both the male and female Mollies are sexually mature, they will breed without much effort from the caregivers. Once the breeding has taken place, the next step is gestation.

Molly Pregnancy Stages

The biology of reproduction in livebearing species like Mollies proceeds a little differently than in egg-laying fish.

A Molly pregnancy can last anywhere from 20 to 40 days. And that gives fish keepers ample time to prepare a separate birthing tank for when the gestation period is nearing its end.

However, if you’re interested in learning how the gestation term progresses from start to finish, this section’s for you:

• Insemination

Livebearing fish carry their fry inside their bodies and give birth to fully-formed fry. That means the process of fertilization of eggs takes place inside the female’s body too.

The male Molly inserts its gonopodium (modified anal fin that also serves as a copulatory organ) inside the female’s anal vent and releases the sperm.

• Egg Development

Once the insemination takes place and the eggs are fertilized, they start growing and developing side the female’s body.

The gestation period of Mollies can last anywhere from three to six weeks. You may also notice the female Molly grow in girth and develop a few behavioral changes during this time.

• Birthing

Once the gestation period is over, your Molly fish will give birth to live free-swimming fry. Unlike egg-laying fish species, these fry don’t have egg sacs attached to them and require looking after and feeding from the moment they’re born.

Also, female Mollies don’t look after their fry after birth and are liable to try and eat them for sustenance. That’s why it’s a good idea to remove the female fish from the birthing tank once the fry are born.

Taking Care of the Fry

Once you’ve set up a separate fish tank for the birthing process, be sure to include a breeding net to help keep the fry safe from momma fish.

Fish keepers can’t keep an eye on the birthing tank at all times, and that’s where a breeding net can help keep the fry safe from being eaten until you remove the female fish from the tank.

Besides that, you’ll have to feed the fry a diet consisting of baby brine shrimp or infusoria to look after their nutritional needs. Don’t attempt to add the fry to an aquarium containing adult Mollies until they’re at least two months of age.

Molly Breeding Behavior

Fish species can be incredibly diverse when it comes to patterns of breeding. If you’re trying to stay on top of your caregiving game, here are some pointers to help you understand that your Mollies are ready to breed.

Before the breeding process can begin, it’s essential for the fish to have reached sexual maturity. In the case of Molly fish, you’ll be able to tell your fish are ready to bring their offspring into the world when they start exhibiting chasing behavior.

While in some fish species, males display chasing behavior, Mollies are unique in that both males and females can chase each other to commence the breeding ritual.

If you’re a first-time aquarist, male or female, Mollies chasing each other can seem a little like aggression.

Polygamous Fish

What’s more, Mollies aren’t monogamous, so if your tank contains multiple males and females, you’ll notice a single male trying to mate with multiple females and vice versa. That’s one reason why Mollies are so extremely easy to breed.

Don’t get anxious if you don’t see your female Mollies exhibit chasing behavior. There’s nothing wrong with your fish.

As long as you notice males chasing the females, you can be sure the fish is ready to mate because female Mollies reach sexual maturity before the males.

What’s more, you may be able to tell when a female Molly is ready to mate when you see her swimming in a vertical position and slow its speed while swimming. That’s the female Molly’s way of signaling she’s ready to proceed to her mate.

Is the Molly Fish Easy To Breed?

The Molly fish is extremely easy to breed. Like Guppies, Molly fish will often reproduce with no direct human intervention.

Mollies (aka Poecilia Sphenops) are livebearers too, which means the female Molly will carry the eggs in her belly, and when it’s time, she will give birth to free-swimming fry. That’s one reason why experts suggest aquarists prepare a separate birthing tank.

This helps ensure the maximum survival for the fry, and the young ones are vulnerable to other fish swimming in the aquarium.

Number of Fry per Birth

A single Molly fish can give birth to as many as 100 fry Mollies in a single go. That means fish keepers who take measures to ensure the survival of as many fry as possible can go from a pair of Mollies to a multitude of them in no time.

Conclusion

We’ve reached the end of our Molly gestation care guide and hope all your queries have been answered. Molly fish are pretty easy to breed and care for, but you’ll still need to take a few measures to ensure maximum fry survival.

Here are some of the highlights of caring for a pregnant Molly and her fry:

• Mollies are livebearing fish and carry the fry inside their bodies. This species gives birth to fully-formed fry that need care and maintenance from the moment they make their entrance.

• Aquarists can tell their fish are ready to breed once the males start chasing the females to breed. This chasing maneuver may seem like aggression to newbies, but it’s a signal that the fish are ready to mate.

• Once insemination occurs, you can tell if your female Molly is pregnant or not by watching out for specific signs. These include a swollen belly, slightly aggressive behavior, taking shelter in hiding spots, and a darkening gravid patch.

• Fish keepers can also keep track of the different stages of pregnancy in order to stay prepared for the impending birthing process. The different stages of a Molly pregnancy include insemination, egg development, and birthing.

• A Molly pregnancy can last anywhere between three to six weeks. It’s a good idea for aquarists to set up a birthing tank and transfer the pregnant Molly to it by the fourth week to help her acclimate.

Fish keepers looking to add to their local Molly population can do so easily if they follow the instructions listed here. Overall, breeding Mollies and looking after the young fry is a straightforward process that even beginner aquarists can take on.