How Many Babies Do Black Mollies Have? - "File:Black Molly 2.jpg" by Marrabbio is licensed under CC BY-SA 3.0.
How Many Babies Do Black Mollies Have? - "File:Black Molly 2.jpg" by Marrabbio is licensed under CC BY-SA 3.0.

Welcome to the captivating realm of mollies, delightful freshwater fish cherished by aquarium enthusiasts worldwide. Among the array of intriguing qualities that set mollies apart, one remarkable aspect stands out: their remarkable capacity for livebearing. In this exploration, we will unveil the secrets behind the prolific nature of these fascinating creatures, delving into how many babies do black mollies have. So, let us embark on this aquatic journey, discovering the wonders of molly reproduction and the mesmerizing spectacle of their vibrant fry, as we unravel the mysteries of how many babies these vivacious fish can produce.

About Black Mollies

Black mollies (Poecilia sphenops) are popular freshwater fish in the aquarium hobby due to their striking appearance and ease of care. As their name suggests, they are known for their predominantly black coloration, but they can also exhibit shades of silver, orange, or yellow on their fins and body.


  • Coloration: Adult black mollies typically have a glossy black color, which may vary in intensity depending on the individual and the lighting conditions. Some may have a velvety or metallic sheen to their black color. In addition to black, some black mollies may display other colors like silver, orange, or yellow accents on their body and fins, creating beautiful contrasts.
  • Size: Black mollies are relatively small fish. On average, they grow to be around 3 to 4 inches (7.5 to 10 cm) in length, with females being slightly larger than males.
  • Sexual Dimorphism: Male and female black mollies can be distinguished by their anal fins. Male mollies have a modified anal fin called the gonopodium, which is elongated and specialized for transferring sperm to the female during mating. Female mollies have a more traditional rounded anal fin.


  • Peaceful Nature: Black mollies are generally peaceful and social fish. They are suitable for community aquariums and can coexist with other peaceful fish species that share similar water requirements.
  • Active Swimmers: Mollies are active swimmers, and they prefer a well-lit tank with plenty of open space to swim around. Providing some floating plants can also help create shaded areas in the aquarium.
  • Omnivorous Diet: Black mollies are omnivores, meaning they eat a varied diet. In the wild, they primarily feed on small aquatic invertebrates, algae, and plant matter. In captivity, they readily accept commercial flake or pellet food, but it’s essential to supplement their diet with occasional treats like frozen or live foods to provide essential nutrients.

Live Bearers and Fry

One interesting aspect of black mollies is that they are livebearers, which means they give birth to live fry instead of laying eggs. The female carries fertilized eggs inside her body, and the fry develop internally until they are ready to be born. The gestation period is typically around 4 to 6 weeks, but it can vary based on water conditions and the individual molly.

When the female is ready to give birth, she will release the fry into the aquarium. These newborn fry are relatively large compared to the fry of egg-laying fish, and they are already capable of swimming and feeding on their own. However, they are still vulnerable, and it’s essential to provide hiding places and proper nutrition for their survival.

The ability to give birth to live fry makes mollies fascinating to observe in the aquarium, and it also contributes to their popularity among hobbyists. Keep in mind that if you keep male and female mollies together, you are likely to experience new generations of fry in your tank, so be prepared to care for and manage their population accordingly.

So, How Many Babies Do Black Mollies Have?

So, you may ask, how many babies do black mollies have? Black mollies, like other livebearing fish, can give birth to a relatively large number of babies in a single brood. On average, a female black molly can give birth to anywhere from 20 to 100 fry (baby fish) at a time. The exact number of fry can vary depending on the individual molly’s age, health, and other factors.

Mollies are prolific breeders, and their ability to give birth to live fry rather than laying eggs contributes to their popularity in the aquarium hobby. If you plan to keep black mollies in an aquarium, it’s essential to be prepared for the potential increase in population and have a plan for managing and caring for the fry as they grow.

How Many Babies Do Black Mollies Have? - "File:Black Molly 2.jpg" by Marrabbio is licensed under CC BY-SA 3.0.
How Many Babies Do Black Mollies Have? – “File:Black Molly 2.jpg” by Marrabbio is licensed under CC BY-SA 3.0.

Raising the Fry

Raising fry can be a rewarding but challenging task. Here’s a step-by-step guide on how to raise black molly fry:

  • Separate Aquarium Setup: As soon as you notice the female molly giving birth or see the fry, you may consider moving them to a separate aquarium. This is because adult fish, including the mother and other tankmates, may eat the fry, posing a significant risk to their survival. You can also choose to move the pregnant mother to a separate breeding tank, and remove her after she has given birth.
  • Tank Size: The size of the separate aquarium depends on the number of fry you have. A 10-gallon tank should be sufficient for a moderate number of fry. Make sure the tank is cycled and has stable water parameters.
  • Filtration: Use a sponge filter or a gentle air-driven filter in the fry tank. Avoid using powerful filters, as the strong currents can be harmful to the small fry.
  • Heating and Water Parameters: Maintain the water temperature around 75-80°F (24-27°C), which works for most mollies. Keep the water clean and conduct regular water changes to ensure good water quality.
  • Hiding Places: Provide plenty of hiding places for the fry, such as live plants, artificial decorations, or commercial breeding traps. These hiding spots offer protection from potential predators.
  • Feeding: Black molly fry should be fed small, frequent meals. The most suitable food for newly hatched fry is infusoria or commercial fry food designed for livebearers. As they grow, you can introduce baby brine shrimp, crushed flake food, or powdered fry food. Offer small amounts of food multiple times a day.
  • Water Quality Maintenance: Regularly monitor the water quality, as fry are more sensitive to changes in water parameters. Frequent small water changes (around 20% every 2-3 days) will help keep the water clean and stable.
  • Growth and Separation: As the fry grow, they may start to outgrow the separate aquarium. Once they reach a size where they are too large to be eaten by adult fish, you can consider introducing them to the main tank. However, keep an eye on the interactions, as the fry may still face some aggression from adult fish.

Remember, raising fry requires attention and dedication. Keeping the water clean and providing proper nutrition are crucial for their survival and growth. With proper care, you can watch the black molly fry grow into healthy adult fish.


In conclusion, the captivating world of black mollies never fails to amaze with its wondrous reproductive abilities. As livebearers, these freshwater fish showcase a remarkable process of bringing new life into the aquarium. With a potential brood size ranging from 20 to 100 fry per female, it’s evident that the molly’s ability to give birth to live offspring contributes to their popularity and intrigue in the aquarium hobby.

As responsible caretakers, understanding the prolific nature of molly reproduction is crucial in managing their population and ensuring the well-being of the fry. Providing a separate aquarium for birthing and raising the fry, along with a balanced diet and optimal water conditions, allows these delicate creatures to thrive and grow into healthy adult fish.

From their striking appearance to their peaceful demeanor and the wonder of their livebearing process, black mollies continue to capture the hearts of aquarium enthusiasts, offering a constant source of fascination and joy for those who welcome them into their aquatic homes. Whether you are an experienced hobbyist or a curious newcomer, the journey into the world of black mollies and their abundant offspring promises to be an unforgettable and enriching experience.

We hope that you’ve found this article about how many babies do black mollies have helpful.