How Do Mollies Mate?

With a tank full of fish, it is evident that at some point you are going to have a pregnant fish in the midst, giving you lots of cute teeny little swimmers to look at - but have you wondered how these critters mate?

Mollies are a fascinating breed and a really popular beginner fish for anyone with a fish tank. They mate and even give birth in a very interesting way, which sets them apart from lots of other fish.

So whether you are new to keeping fish and are interested in breeding one of the most popular fish out there, or whether you are here out of sheer curiosity, or even if you have a pregnant molly and are wondering how on earth that happened, keep on reading.

We will tell you all there is to know about how mollies mate in this article. 

The first thing to note is that mollies are livebearers. This means that rather than laying eggs for their babies to hatch from like most tank fish, they give birth to live fish (also known as fry). The female mollies have a sexual cycle that is around a month.

They can also store sperm in their bodies for this time, too. Male mollies, on the other hand, are known to be very promiscuous in the fish world and engage in sexual behavior daily. 

The conditions in your tank must be perfect in order for mollies to breed. The water should be very clean, as well as the tank in general being clean. Many experts recommend raising the temperature of the tank very slightly, but ensure that you never exceed 78 degrees Fahrenheit. The slight rise in temperature can encourage the mollies to mate. 

As it is also known that female mollies tend to prefer larger male mollies for copulation, it is important to ensure your male mollies can grow big enough if you want to breed them.

To make sure that they grow big enough you should feed them very good quality flaked foods, as well as the occasional feeding of bloodworms and live brine shrimp. All of these will encourage growth and good health in your mollies. 

In terms of how many males you would need, don’t worry about giving each female molly its own partner. Mollies are polygamous, and so they will often copulate with each other.

For this reason, the ratio of female to male fish is one male for every three females. The male will be the fertilizer of all the mollies’ eggs. Be aware that any more male fish added into the tank can result in too much stress being placed on the female mollies.

This can in turn cause them not to reproduce as quickly as they can and can result in aggressive behavior from all the fish in the tank.

The same should be said about other breeds of fish. Consider what tankmates you keep with your mollies when you want to breed them. In fact, when you want to breed your mollies, it is highly recommended that you use a separate breeding tank to contain your three female fish and one male fish. 

Then, when you have your pregnant mollies, it is important to protect the offspring from being eaten by the adult fish. To do this, any female molly that is pregnant can be kept in a breeder box.

These are boxes that have holes small enough for the young fish to get out but keep the adult fish away from them as they cannot fit through the holes. This will allow young mollies to grow and reach maturity.

You can feed them high quality smaller flakes until they are big enough for proper food. 

When it comes to the act of mating, there are two ways that the males tend to attempt it. One way is through performing a courting display. It sounds very traditional, doesn’t it?

It’s not quite like the courting of the olden days though, there’s no ballroom dancing and stolen kisses. Rather, the male mollies display in front of the females who will then allow them to copulate.

The copulation of mollies involves the male fashioning a penis-like copulatory organ that comes out of the anal fin. The organ is called the gonopodium. It is positioned underneath the male, and when the male is about to copulate, you may notice that the anal fin starts to bend the opposite way as it chases the female. 

The second way that mollies mate is through the male sneaking up on the female aggressively, this is called sneak-copulation and is done when the female is unaware by him sneaking up in an area that her vision does not reach.

The female molly can then choose to store the semen until a later date or to allow her eggs to be fertilized right then.  The molly can store the semen for a lengthy period of time, which is why you find that mollies seem to be able to give birth even when a male is no longer in the tank. As well as this, it can take between 35 to 45 days for the female molly to give birth to these live offspring.

Final Word

As you can see, the breeding of mollies is a particularly interesting one and sets them apart from much other tank-kept fish. We hope that this article has answered your question of ‘how do mollies mate?’, as well as answering some other sought after queries.

These promiscuous critters can copulate like there’s no tomorrow and can do so by courting the female molly until she allows fertilization, or even by sneak-copulation which is an aggressive attack on the female molly.

The male molly uses a penis-like organ called the gonopodium that comes out of the anal fin, and amazingly, the female mollies give birth to a live baby fish (or fry). The whole process is scarily similar to human procreation. Maybe we are all closer to being mermaids than we think….