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How to Tell If a Neon Tetra Is a Male or Female?

Neon tetras are one of the most popular fish in the world. When given proper care, these social, colorful fish make fantastic additions to peaceful community tanks.

The charming nature of these fish makes it tempting for hobbyists to learn how to sex neon tetras. While many guides exist on sexing neon tetras, the first step usually requires one to tell the difference between male and female neon tetras. 

Distinguishing between a neon tetra male vs. female can be challenging due to their minuscule size. Thankfully, telling them apart is easy if you know what to look out for!

What is the Difference Between a Male and Female Neon Tetra?

Female neon tetras have a more rounded belly, causing the shape of their horizontal blue stripe to appear curved. Meanwhile, male neon tetras are distinguished by their slender bodies, straight blue stripes, and brighter colors. In many cases, males have longer dorsal and anal fins compared to their female counterparts.

Male Tetras vs. Female Tetras

Factors

Male Neon Tetra

Female Neon Tetra

Neon tetra in planted aquarium
Neon tetra ( Paracheirodon innesi ) photographed in an aquarium

Shape of Blue Stripe

Straight

Curved

Color

Brighter

Less Vivid

Body Shape

Slender

Rounded

Belly

Flatter

Larger

Length of Fins

Longer

Shorter

Male Neon Tetra

Neon tetra in planted aquarium

Shape of Blue Stripe

Straight

Color

Brighter

Body Shape

Slender

Belly

Flatter

Length of Fins

Longer

Female Neon Tetra

Neon tetra ( Paracheirodon innesi ) photographed in an aquarium

Shape of Blue Stripe

Curved

Color

Less Vivid

Body Shape

Rounded

Belly

Larger

Length of Fins

Shorter

If you were hoping to tell neon tetras apart at a glance, this might be a harder task than you anticipated. 

It is virtually impossible to tell male and female neon tetras apart before they reach sexual maturity. After about 4-6 months, you may begin to spot subtle differences between the boys and girls. Even so, this takes a trained eye (and perhaps a magnifying glass!)

Neon tetras feature minimal sexual dimorphism, so the physical differences that exist between male and female fish are minimal and subtle. Here’s a direct comparison to help you distinguish between the two!

Shape of Blue Stripe

Neon tetras are named after the neon blue stripe that runs lengthwise down their bodies. The shape of this blue stripe is one of the easiest ways to tell males and females apart.

Neon Tetra Paracheirodon innesi freshwater tropical fish

On the slender bodies of male fish, this blue stripe appears relatively straight. However, this neon blue line takes on a curved appearance on females as they have a rounded body shape.

Color

While both male and female neon tetras bear distinctive blue and red stripes over their iridescent bodies, male neon tetras have colors that are more vivid and vibrant compared to their female counterparts. 

Male neon tetras have evolved to feature distinctive and vibrant colors as they compete with one another for the female’s attention. 

Body Shape

Size differences can be difficult to discern on neon tetras because they are tiny. However, this task is made easier by the fact that the size difference in neon tetras also results in distinctive body shapes.

Male neon tetras have a relatively slender body, while female neon tetras have a more rounded body shape. Female neon tetras also tend to look a little larger and longer. 

Belly  

Compared to male neon tetras, females have a larger belly. Neon tetras are egg spawners, so the larger bellies on female fish do not indicate pregnancy. However, it can mean that they are ready to spawn, particularly if your fish’s belly appears larger than that of her tankmates.

If you were intending to breed your fish, now would be a good time to transfer the breeding pair into a separate tank.

Length of Fins

In general, male neon tetras have longer dorsal and anal fins than the female’s. This is a good way to distinguish between males and females in a tank containing similarly-shaped neon tetras.

One thing to bear in mind is that some neon tetras have been selectively bred to have longer fins. If this is the case, simply use some of the other features listed above to aid you in your quest!

Captive-Bred Neon Tetras

Neon tetras are sometimes captive-bred to obtain a greater variety of physical traits. As mentioned above, some have been selectively bred for longer fins. However, this doesn’t even begin to scratch the surface of the many types of neon tetras available!

What Does a Wild-Caught Neon Tetra Look Like?

Wild-caught neon tetras are considered true variants. Most captive-bred neon tetras look like their wild counterparts. The natural appearance of a neon tetra features:

  • A neon blue stripe running down the top half of its body, including its back
  • A silvery, iridescent belly
  • Moderately-sized fins
  • A bright red stripe extending from its tail fins to anal fins

Ornamental Neon Tetras

To keep up with the immense popularity of these fish, ornamental strains of the neon tetra exist. They are selectively bred for physical traits that give them a distinctive look. Though these are still neon tetras, they can look very different from what you would expect.

Here are some of the different types of neon tetras available:

  • Diamond Head Neon Tetra
  • Double Longfin Neon Tetra
  • Brilliant White Neon Tetra
  • Gold Neon Tetra

Because ornamental neon tetras can look a little different compared to the true variants, it can be a little harder to tell males and females apart using the guide provided above. Traits such as coloration and fin length may no longer apply to selectively bred fish.

Identifying Gender in Ornamental Neon Tetras

There are, however, a few things that remain constant about males vs. female neon tetras no matter what the strain. The key thing to look out for is body shape. 

Male neon tetras have a more slender and streamlined figure, while females have a rounded, larger shape. These differences remain evident even in selectively bred fish. Breeders usually retain this physical trait because body shape, unlike color and fin length, plays a fundamental role in reproduction.

Green Neon Tetra underwater
Image Source: commons.wikimedia.org

So, even if you find yourself with a unique-looking neon tetra on your hands, you can rest assured that you’ll still be able to tell the males and females apart. Just take a close look at the shapes of their bodies, and you’re set!

Conclusion

Whether you’re just curious or hoping to sex your fish, it is useful to learn the difference between male and female neon tetras. 

The popularity of these fish makes them a staple in most freshwater tanks, which gives you plenty of opportunities to put your newfound knowledge to good use!

If you’ve enjoyed learning more about these gorgeous fish, don’t forget to share this article with someone else who might enjoy it. As always, we’d love to hear your thoughts in the comments!

Wanda is a second-generation aquarist from the sunny tropics of Malaysia. She has been helping her father with his freshwater tanks since she was a toddler, and has fallen in love with the hobby ever since. A perpetual nomad, Wanda does her best to integrate fish-keeping with her lifestyle, and has taken care of fish in three different continents. She loves how it provides a nice break from the hustle and bustle of life.

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