How to Tell if Guppy Fry is Male or Female?

Guppies come in two sexes, just like most other animals. They are male and female, but for most people, it’s quite difficult to differentiate between them. However, expert fish keepers would tell you that it’s simple enough to recognize a female from a male guppy.

But this only works in adults because their physical characteristics are more visible. Guppy fry are indistinguishable from one another at that stage, so you won’t be able to make sense of their sex.

If, for any reason, you want to know how many males and females you currently have, this article should help you out. I’ll give you a few techniques to quickly figure out if a guppy is male or female. Moreover, I’ll explain why baby guppies should be separated by gender!

When’s The Best Time to Notice Sex Differences in Guppies?

Every new beginner will ask this question, and it’s only natural that you encounter problems at first. After some research, though, you should discover the differences between male and female guppies. As they grow up, the fish will start to look a bit different based on their sex.

Of course, when they’re just born, all guppies look the same. There’s no way you can know which is male and which is female. Even as they grow up, the differences will be very subtle at first, and a novice will likely not notice them. But as the guppies grow up, the differences become more evident.

At about 4 weeks, the guppies will start to look different based on sex. In other words, one month of age is just enough to spot those differences and identify males from females. If you’re especially close to your guppies, you may have noticed a few differences even before this period.

Identifying the sex of your guppies is essential, whether you plan to sell them or if you’re doing it as a passion. For instance, you may not want your guppies to breed, thus avoiding overpopulation issues. So, you’ll need to separate males from females. But you can’t do that if you can’t identify the two sexes, right?

Even if you won’t separate them outright, instead preferring to keep them mixed up, you’ll still need to know the male-to-female ratio. Maintaining control over a mixed tank with an unknown male-to-female ratio is beyond difficult.

I usually recommend keeping one male to 2-3 females, and even then, you should understand that they’ll breed constantly. Hundreds of guppy fry will be born after every successful mating. You should control the breeding frequency by limiting the number of females, because constant mating harms your guppies’ lifespan.

Lastly, if you want to sell your guppies, you’ll need to separate them based on gender. People will want to buy males or females, and you may want to sell them as such!

Why Do You Need to Separate Guppy Fry By Gender?

A separation of guppy fry by gender is not only needed to sell them or have them breed faster. Knowing which is a female or a male also helps with their growth rate. When guppies reach maturity (around 3 months old), they’ll be mating. And as you know, mating consumes many resources, slowing down their growth.

If you want to stop them from mating, you’ll need to separate male guppies from female guppies. Assuming you want them to grow as fast as possible, you’ll want to prevent them from mating at all costs.

But separating guppies based on sex isn’t the only way you can improve their growth rate. Give them enough space through a larger aquarium, especially if you have a large population of guppies available. Vary their diet and make sure the food is of high-quality. Lastly, make sure the water is well maintained and clean.

It’s important to use all methods at your disposal that can improve the growth rate of your guppies.

How Can You Tell Between Male and Female Guppies?

As I said, if you’re a beginner, you’ll find it hard to spot the differences between male and female guppies. But as you take a closer look, you’ll see them. After some time, you won’t have anymore problems separating your guppies based on sex.

Females are generally larger, longer, and less colorful than males. Their abdomens are also larger because of their big bellies. On the other hand, male guppies are smaller, more colorful, and have more beautiful tails. Their anal fins are long and pointed, unlike those of females, which are smaller and squatted off.

Guppy fry are almost impossible to differentiate based on sex because the differences are minuscule. But if you use a magnifier, then you’ll eventually figure out if the fish in your hand is liable to give birth or not. To identify males and females in guppy fry, you should:

– Identify the gravid spots in females

All females have gravid spots at the end of their tails. That’s the location where the fry will grow when the female guppy becomes pregnant. This spot is darker in color and it’ll become more evident once the female grows older.

If the guppy is a female, you’ll notice the swollen, darker spot near the anal fins. That’s the gravid spot!

– Look for the gonopodium in males

While females have a gravid spot at their anal fins, males have a so-called gonopodium. Think of it as the penis of the fish. It’s what males use to impregnate and fertilize females. Though, fertilization takes place differently in livebearing fish like guppies. Everything happens inside the female, including the hatching of the eggs.

Most importantly, guppy females will give birth to hundreds of fry at the same time, which will eventually lead to overpopulation and overstocking problems in the aquarium. If you want to correctly identify the gonopodium in males, you’ll need to wait 2-3 weeks before trying.

Once the males develop their gonopodium, you’ll have no problem identifying it and differentiating it from the gravid spots of females. One more thing you could use to identify males is watching for fish that are chasing other fish. Most likely, those are the males chasing after females.

Males are also more colorful and smaller than females, but this only becomes clear after 3 weeks. That’s when the natural colors of males become more vivid and quite different from those of females.

If your fish only has a slightly colorful tail, then it’s a female. If the colors have started spreading on the body, then you’re dealing with a male. Color development in guppies signify the traits of a male.

Many people are thus inclined to keep more male than females, thanks to their vivid colors. This is a good idea, since keeping a mixed tank will result in fry being born. If you don’t want to deal with overpopulation issues, then I recommend keeping males only. Females aren’t as beautiful as males, and they’ll also give birth to hundreds of fry at once.

Will Females Grow Quicker Than Males?

If you’re not a complete beginner when it comes to breeding guppies, you may have noticed that some fry grow faster than others. One of the factors that contribute to this change in growth rate is sex. Females tend to grow faster than males.

But that’s not a general rule. Among males, those individuals that mate less and have access to more food will grow faster. Moreover, you should also separate the bigger fish from the smaller individuals. If adult guppies eat all the food, the fry will have no nutrients to grow from.

It makes sense that you keep the fry separated from the adults, in a separate tank. Keep them there until they grow up sufficiently, or until you can sell them. When they become adults, you can release them in the main tank.

Wrap Up

At first, it’s only normal that you can’t differentiate between male and female guppies. This skill takes time to develop, and if you spend more time with your guppies, it’ll become second nature to know which is female and which is male.

Some fish don’t exhibit sexual dimorphism, which means the physical differences will be almost non-existent. However, guppies are easily recognized by gender, based on other factors than physical ones. Behavior is one such characteristic that almost never fails. Males tend to chase after females to mate, for instance.

All in all, identifying the gender of your guppies comes in handy, whether you’re doing it as a hobby or if you plan on selling them. Moreover, if you have a mixed tank, you need to control the population carefully. If the females give birth to too many fry, you’ll have an overstocking problem on your hands.

You can also improve the growth rate of guppies if you know how many males and females you have. To prevent a decrease in growth rate because of mating, I recommend a 1-to-3 male-to-female ratio. In my experience, this provides the best results over the long-term.

If you have any questions, leave them below and I’ll reply within minutes!

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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