Molly Fish Gestation Period: Pre And Post Natal Care

Once in a while, you need to check on your molly fish to make sure they live their lives happily in captivity. And the bliss you feel the moment you see them pregnant is something you can’t put in words. But waiting to see the fry in the tank makes you eager, excited, and impatient. So, you counteract this feeling, knowing the molly fish gestation period helps; well, it helped me. So, how long are moly fish pregnant for? What is the gestation span of your mollies?

Molly Fish typically has about 20 to 40 days of gestation period. When the mating process ends, it takes anywhere from 3-5 days for the eggs to develop into fry, and it will take 15 to 35 days before female mollies give birth to live fry. But it can stretch up to 60 days when it comes to dalmatian mollies.

The gestational period is important if you want to breed your Molly fish. Thus, this post will be a perfect guide for molly owners.

What Is A Gestation Period?

Molly’s gestation period is when she will spend carrying her young. This varies depending on the species of Mollies, age of fish, and other factors.

It is important to note that the gestation and incubation periods are not necessarily the same. The gestation of a fish or other aquatic animal can directly impact how long it takes for her eggs, embryos, and young to develop outside of their mother’s body.

Molly’s gestation will be longer than the time spent developing inside her body.

What Type Of Fish Is Molly Fish?

Mollies are members of the family Poeciliidae, which is a live-bearing tooth carp.

This fish has many different species. While they vary in appearance, among other things, one commonality is that mollies give live birth instead of giving eggs like most types of saltwater or freshwater fish.

Mollies are also famous as Mexican Molly, black Molly, or by their scientific name Poecilia sphenops. This fish is native to the southern United States and northern Mexico.

But now traveled to other regions of North America (notably Florida), Central America, South America, and Asia. Thus, Mollies are now present worldwide.

How Do Molly Fish Reproduce?

Mollies are live-bearers and reproduce by using their viviparous,  a.k.a., a live-bearing system where the female gives birth to her young alive rather than laying eggs and letting them hatch outside of her body (as with egg-laying fish).

Male molly fertilizes the eggs internally as they develop inside the female’s body. The eggs develop inside the female Molly fish until they are ready to hatch, at which time she gives birth to them live and in person.

The fry comes out very small but otherwise completely formed, even having their yolk sacs for a short period after birth to continue developing and growing.

The female Molly fish then repeats this entire process repeatedly until she dies or the male can no longer fertilize her eggs due to old age/health reasons (she will most likely lose interest in mating).

How Long Does Gestation Period Lasts In Molly Fish?

For a pregnant molly fish in a pet store with no idea what kind of Molly she is (and doesn’t bother to ask the owner), they often guess around 28 days just because it’s not too far off from 30-40 days.

It’s better to estimate that way than get the molly fish owner mad at you for saying she is pregnant when she isn’t/giving false hope if she wasn’t.

With live-bearing fish like Mollies, gestation is longer because they don’t release their fry until they develop fully. As a result, they can have a gestation period that lasts anywhere from 40 to 60 days!

The average molly pregnancy is about a month and a half from mating until birth. And if you are handling dalmatian ones, you have to wait for nearly 70 days to see fry in the tank.

What Are The Factors That Influence The Gestation Period Of Molly Fish?

As mentioned earlier, the gestation period of molly fish can vary depending on factors such as water temperature and other environmental conditions. The average time to give birth is around five weeks or 20 days after mating with males ready to fertilize their eggs. However, there have been cases where this duration has lasted several months.

So, the factors that influence the gestational period of Molly fish are:

Water Quality

The water in which the mollies live is critical for determining their gestation period. For example, contaminants or pollutants present in the water they reside in will increase the time needed for them to become fertile and hence give birth after mating with males of a similar kind. This is because these contaminants threaten the fish’s natural immune system and cause them to become weak.

Water Temperature

Water temperature is the main factor that influences Molly’s gestation period. It can range anywhere from 72 to 78 degrees Fahrenheit, with 75 ideal for breeding. However, if the water is too cold, it will lengthen the gestation period while warmer waters shorten it.

Fish Food

The quality of fish food also significantly impacts Molly’s gestational period, ranging from 21 to 30 days after mating with males ready to fertilize her eggs. However, there have been cases where this duration has lasted several months.


The older the female fish, the longer her gestation period will be. Once she reaches 4 to 5 years old, expect her to give birth after around six weeks of mating with males ready to fertilize her eggs.

However, there have been cases where this duration has lasted several months. In addition, older mollies often die after giving birth to young ones as they are weak and sensitive after repeated pregnancies.


There are several types of Molly fish, and each one has a different gestation period. For example, the standard mollies can give birth after 20 to 40 days of pregnancy, while the dalmatian Molly takes about 70 days to deliver the fry.


If the female mollies are generally unhealthy, this will negatively impact their gestation period. Females with parasites or diseases usually take longer to reproduce than healthy ones.

How To Take Care Of Pregnant Molly Fish?

Pregnancy is a crucial stage for Molly fish, so identify if your molly fish is fat or pregnant first. Both increase and decrease in its gestational period can cause complications. So, there are some things to consider when taking care of pregnant Molly fish. Such as:

Separate Pregnant Molly Fish

Pregnancy can make any living being weak, vulnerable, and sensitive. So, it is better to give them an environment where they will feel safe and happy.

Keeping molly fish happy is not that hard; just find a new tank for these pregnant fish where no tank mates will bother them.

Size Of Tank

It is better to increase the size of an aquarium to keep mollies comfortable and happy. However, it does not have to be as big as a tank during pregnancy, but you will need more as time goes by.

In other words, an appropriate-sized tank for molly fish is often 20 gallons or larger during and after pregnancy.

Water Condition

Mollies are not picky fish at all. However, it is important to keep the water clean since molly’s pregnancies are sensitive.

Molly owners should ensure their pregnant fishes have clean water by removing waste daily and regularly changing the water of aquariums for molly fish by 50% of their total volume every week.

Also, ensure that the water is free of toxins and contains natural salt. These are necessary for pregnant Molly fish to prevent infection and stress during pregnancy.

Adjust The Tank Temperature And pH

It is also important to adjust the ideal water temperature for molly depending on the molly fish breeding cycle. For example, the best tank conditions for pregnant molly fish would be at 78-82°F or 26-28°C.

You must maintain the pH at a range of around 7.7-8.2. However, pregnant molly fish can survive in a wide range of conditions, with pH levels extending up to 8.3 or down to 6 depending on whether it’s summer or winter.

Food Consumption During Pregnancy

Mollies are omnivorous fish. Therefore, they can eat plants and other small meaty stuff to survive in the wild. However, it would help if you fed pregnant molly fish with high-quality foods which contain vitamins A, B12 & DHA/EPA fatty acids for healthy babies.

Depending on their appetite, it would help if you fed pregnant mollies once or twice a day. However, fish owners should provide them with small amounts of food to avoid overfeeding, leading to water pollution and other health problems for the fish.

Introduce Plants And Decorations

In addition, feeding pregnant molly fish high-quality foods is also important for having a healthy environment.

In other words, you should introduce plants and decorations into the tank that are appropriate for both Molly fish and babies.

Plants would help improve water conditions, while baby Mollies might eat some of them. So, you understand molly fish needs live plants in the tank, but please remember to use very few of them. Your mollies hate a densely planted tank with no space to swim or play around.

General Health Of Mollies

It would be great if Molly owners could provide pregnant fishes with lots of hiding places and plants in their aquarium. However, it is unnecessary to do so if you cannot provide them with such things because the most important thing is keeping your pregnant molly fish safe and sound.

Some FAQs

How Long Does a Molly Fish Pregnancy Last?

The gestational period for a molly can range from 21-40 days, after which they give birth to live babies. They have about ten babies or more in one litter. It may take them about 20 days to grow fully.

Is It Possible for a Molly Fish to Get Pregnant Without Sex?

Yes, it is possible but not very common. Some female mollies get pregnant without having sex because sometimes, after mating with the male, some females store sperm in their body instead of releasing it.


Summing up, we can say that the gestation period of a molly fish varies. There is no one specific time for this to happen. Instead, it can range from 24 hours to over 50 days. The average, though, is around 30-40 days. However, please note that these are guidelines only, and it depends on many factors such as water, food, tank size, and environmental conditions.

Hopefully, this blog post has cleared some of your doubts about Molly’s gestation period.

Good Luck!!!

Happy Fishkeeping!!!