Do Molly Fish Change Gender? (Why They Do)

Do Molly Fish Change Gender?

It has been scientifically proven that up to 500 Species of fish could be able to change their genders due to various reasons, but the question is, ‘ are Mollies one of those types of fish?. There is a serious argument about this issue, some do say that they can change their genders, while others say, they don’t. If you are still confused, then read this article slowly to comprehend and clear your doubt.

Do Molly Fish change gender? Yes, they could change their gender when it suits them.

I have read many theories about this, and when I say they do, am talking from. experience, because it has happened in my tank twice.

It is not uncommon for fish to change their immediate gender, or sex to that of the opposite. Many fish are said to do this, such as guppies, and some species of Goby and platy, etc. So it shouldn’t be a new thing if Molly fish do the same.

Mollies are livebearing fish, and not hermaphrodites, although the majority of fish that could change their sex are not livebearing fish and they are hermaphrodites, meaning they could reproduce without the presence of a male.

Fish don’t just wake up one day and decide to turn to the opposite sex, there are some reasons why they do that, and we shall discuss all of them in this article.

Why Molly Fish Could Change Gender

Some of the possible reasons why they might decide to change gender are:

1. When their existence is under threat of extinction.

It is believed that one of the most common reasons why animals could change their gender is when their existence is facing extinction.

For instance, if there are more female mollies in a tank or water, some of them might likely transform into males, to mate and reproduce.

For the fact that they are not hermaphrodites, they will in one way or the other continue to be in existence by reproducing.

So, to continue to exist, some will change to the opposite gender and mate to reproduce.

Apart from fish, this act could even be seen in some birds too.

2. Another reason why they could change gender is when they are Stressed.

Mollies naturally don’t like stress, and when exposed to it might have some health effects on them.

They could easily change their gender when they are overwhelmed with stress, for instance, if a female Molly is constantly being embarrassed by the males, she might have to change her gender to curb some stress she is getting from the males or the other way round too.

3. Sometimes we might even mistake the two genders, like seeing the male as a female, and the female as a male.

This happens sometimes, especially when they are still growing.

So, you might end up being puzzled, seeing the so-called male being a female and vice versa. So, it Happens sometimes, and it doesn’t necessarily mean that that particular fish changed its gender.

How Can You Tell The Gender Of Mollies?

I believe this article can’t be complete without telling you the difference between a male Molly fish and a female Molly.

How can you to the gender of Mollies? Male Molly fish have a long anal fin known as the gonopodium, which they use for mating, while the female Mollies have bigger stomachs than the males.

So differentiating them is very easy, but in some cases, some males will look like the females, while the females will look like the males.

This sometimes happens when they are still. growing, and haven’t fully formed or matured.

Do Male Molly Give Birth?

No, Molly fish are not hermaphrodites, hence they have two different genders. The female gives birth, while the male is responsible for fertilizing the female to give birth.

Although they could change their genders, they can’t give birth, hence they are males, and the females can’t fertilize hence they are still females, until they change their genders, and have the necessary sex organs that they need to mate.


Mollies could change gender when necessary, so, it shouldn’t come as a surprise to you.

Although many people doubt this, it is true, they can.