Black Molly Fish Male And Female: How To Determine & Important Notices

One of the most critical aspects of breeding aquarium fish is figuring out the sex of molly fish, and black molly fish in particular. What is the simplest way to tell male and female black molly fish apart in terms of appearance? How is males behavior different from that of another gender? The question is, how can they raise their fry to be more powerful? And now that you know that, what should you do and what should you avoid?

Here are the answers to all of these questions and our recommendations for solving them. I sincerely hope they are beneficial.

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Determine Black Molly Fish Male And Female

Features Of Black Molly Male

Black Molly Male
Black Molly Male

Black Molly males are smaller than females when considering their body size. The range of them is about 2.5-3.5-inches. Also, their body shape is flat. 

If you look for the difference in their color, I’m afraid that can’t be shown clearly. Honestly, both males and females appear in vast levels of black hue.

How about the dorsal fin which is the back fin visible in your adoring Molly fish? I see that males often have a larger dorsal fin than females. If a guy has a larger dorsal fin than his rival, he takes a big advantage in a mating battle. A big dorsal fin threatens other males, and also attracts his mater. 

Besides, males have a thorn-shaped anal fin. Opposite the dorsal fin, the anal fin is the part of the Mollies body that you can spot underneath, between the pectoral fins and tails, following the stomach area. Their anal fin remodels into a tube-like structure; called; Gonopodium. Through this, they copulate with the female Molly fish.

Features Of Black Molly Female

Females have the opposite traits of males. A female has a rounded body and seems larger than a male, and she can grow to a maximum size of 5 inches. 

Females have shorter dorsal fins when compared to males.

About the anal fin, female guppy fish has a rounded anal fin shape which is in triangular form. 

 Black Molly Female
Black Molly Female

Black Molly Fish Male And Female’s Courtship: Behavior When This Happens


The alpha male’s fins will be more visible than those of the subordinate males. The dominant molly will always have priority access to food, which means he will always have a greater opportunity of mating with available females. He will either chase people away or cause them to flee as he approaches. Females will be more receptive to him as a mate, and he will chase away competitor males as well.

Males can be extremely aggressive and tend to fight for being a winner and mating with females, or for having their own territory. But keeping 5 or more guys actually reduces the bullying of lesser males since the bullying is distributed among all the males in the pack.


Males make every effort to demonstrate damaging behavior, yet not every mating leads to the female being successfully fertilized. The probability of success is approximately 10%. As a result, males are constantly attempting to replicate the procedure in order to ensure the female’s conception.

If the female is uninterested in mating, she will make a concerted effort to avoid the male’s gaze. Given that males are almost constantly attempting to mate and that you may encounter multiple men attempting to mate with a single female, it is preferable to give several females for each male while also providing bushy bushes for females to hide in when they need a break.

A fascinating fact is that if a mature man is present, females can be fertilized extremely early. Furthermore, sperm can be stored for the next 5-6 months. If the fertilization continues, which it does in a mixed tank, the new sperm will certainly fertilize some of the eggs, but the extent to which the first, original insemination can be superseded by a later one has never been fully worked out.

Males are displaying signs of conflict, not mating

There are 3 common signs that prevent you from misunderstanding, include:

  • The male is biting the other fish with his mouth.
  • Rather than attempting to pull up alongside the other fish, the male is driving it into a corner.
  • Rather than circling all the females, one fish repeatedly attacks an individual fish.
How to identify male vs female molly?
How to identify male vs female molly?

Pregnant Black Molly Female: The Information That We Bring To Your Attention


There’re 4 signs that will be listed below.

  • The first symptom is a swollen and stretched-out belly. However, if they suffer from conditions that cause bloating, they may become perplexed.
  • She eats more than usually does because she needs lots of energy for the fry and bearing period. 
  • She seeks warmth by moving closer to the tank’s heating system or temperature stabilizer.
  • She seems not active like daily does. You can observe that she swims slowly in the middle tank and tries to hide from others as much as possible. The reason here is to avoid dangers.

Molly fish normally give birth to a fetus every 50 to 70 days, on average. If the molly has a lot of places to hide, the time it takes to breed may be shorter. The gestation time of some molly species, such as sailfin mollies can be as brief as 21 days.

Your molly fish’s odds of bearing a child are limited if she has been pregnant for 70 days or more. Since you can rarely tell when a fish was conceived, it is impossible to determine how long the fish was pregnant.

What you need to do

Pregnant women should be separated as soon as they show signs of pregnancy, which is the best time to do so. A pregnant black molly will not feel safe if you make changes to her environment too late or if you make the changes without being gentle with her. The fact is that she has a hard time adjusting.

Make sure she has somewhere safe to hide if she gets into any trouble. When all else fails, turn to your trusty houseplants. If you want to prevent a pregnant molly from eating her fry, you should put up a physical barrier. Also, pregnant women will feel more at ease if they have a variety of places to hide.

When a livebearer is pregnant, she will eventually become lethargic and stop eating. However, starving them is not an acceptable excuse. You don’t have to alter their diet because they still need nutritional meals. A variety of foods can be consumed by these fish. Quantity is the most critical factor to take into account.

Rather than feeding these creatures two large meals a day, you should feed them several smaller meals throughout the day. If you don’t, you’ll fill your tank to the brim with waste. Because they are so slow, the creatures are unable to compete for food. No matter how hard you try, you cannot make them eat. They will eat more if you make it easier for them to get to the food.

The aquarium needs to be kept in the proper conditions. A healthy molly’s health can be jeopardized by using water that is of low quality. Having pregnant fish in your aquarium is not a good idea. As a result of their exhaustion and exhaustion, they have become less active. In extreme cases, they may choose to terminate their pregnancies.

How To Raise Black Molly Fry

Mollies can coexist peacefully in the same tank with other species and even breed with one another. Mollies, on the other hand, eat whatever they can fit in their mouths. They also include their own children. Floating plants, dense foliage, and small caves and crevices inaccessible to fully grown fish should be provided in your aquarium for hiding places for fry. Another option is a breeding cage that allows the fry to fall through to an area their mother cannot reach.

Video: How To Determine Black Molly Male And Female


How many black mollies should be kept together?

Black Mollies are generally peaceful community fish, but multiple males kept in the same tank can become aggressive, and females which are outnumbered by males will tend to be harassed. The optimal ratio that we recommend is 3 females to each male.

How many babies do black mollies have?

Female mollies will gestate their young for about 60 days. They can give birth to between 40 and 100 fries. Mollies who are young or have one of their first few pregnancies will tend to give birth to a smaller rather than larger number of fry.

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