How To Tell If Your Glofish Tetra Is Male Or Female?

gender of GloFish

Glofish might come in different colors and varieties, but determining their gender can be tough anyway. And, if you are aware of the fact that breeding glofish and selling the fry is illegal, you might want to know the gender of your glofish tetra to stop it from happening. So, the question lingers; how to tell if your glofish tetra is male or female?

Gender determination can be rocket science when it comes to GloFish. You can only differentiate them with the help of their body structure along with a specific line once they hit sexual maturity.

It can quite difficult to distinguish them beforehand until and unless they are mature enough and not young.

Let me help you, I know this can be confusing. I have made it easier for you with the steps to follow one by one. You will distinguish them in no time.

Glofish Tetra Gender: How To Tell If Your Glofish Tetra Is Male Or Female?

It might take a while before you get a hold of gender determination in GloFish since it can be quite tough.

Don’t worry, I am here to help and make your life a little easier. I know it can be scary when the word “illegal” intervenes with breeding while raising a beautiful fish like GloFish.

So, it becomes quite important to know if you have both males and females in the tank. You can’t control the natural phenomena, but at least you will be prepared for the rest.

Your glofish, be it male or female, will look exactly the same prior to sexual maturity, so you need to wait till they mature.

Now, coming to the point, Let’s differentiate the GloFish Tetra you have in your tank, shall we?

Step 1 Lighting

First thing first, get a good aquarium light for your Glofish tetra tank. You see, looking at the traits and physical features in a well-lit environment is easier.

GloFish Cycle Light From Tetra or All Glass Aquarium Fluorescent Strip Light can help you achieve that; fluorescent or natural lighting is appropriate for this very purpose.

Step 2 Cleaning The Tank

Clean your tank. This is the most vital step in keeping fish but also plays an important role in determining the sex of Glofish.

If you’re a proud owner of Glofish Tetras, you know how important it is to maintain a clean and healthy environment for your fish to thrive. A clean tank not only keeps your fish healthy but also enhances the overall beauty of your aquarium.

To start, you’ll need to invest in a good aquarium gravel cleaner. The gravel cleaner will help remove debris and waste accumulating at the tank’s bottom. Begin by unplugging any electrical devices in the tank and then start siphoning the gravel. You’ll notice the waste being sucked up and out of the tank. Continue cleaning the gravel until the water appears clean.

Next, you’ll need to clean the tank walls and ornaments. Use a clean aquarium sponge or scraper to gently remove any algae buildup from the sides of the tank. Be careful not to scratch the glass or acrylic. You can also remove any decorative items, plants, or rocks and rinse them with warm water.

After cleaning the tank and all its contents, it’s time to replace the water. Start by refilling the tank with conditioned water at the same temperature as the water in the tank. Remember to only fill the tank up to the recommended level to avoid overfilling. Lastly, plug in any electrical devices that were unplugged earlier, and you’re done!

Get a good filter like Penn Plax Cascade 400 Submersible Aquarium Filter and perform water change once a week or every couple of weeks.

Step 3 Observe The Glofish

Now, this is a vital step for determining the sex of glofish, so read the lines and instructions carefully.

Now look closely for the stripes present in the body of GloFish. You might find a blue stripe, a primary stripe that is mandatory in all the glofish, whether male or female.

So, leave this stripe behind, and look closely for the secondary stripe that will help you determine the gender of glofish.

Step 4 Differentiating The Sex Of Glofish Tetra With Stripes

Now, observe the color of the second stripe in the body of glofish. If you see golden stripes on their body, then you are looking at male glofish.

But if the stripes or the second line are silver, the glofish you observe closely is female. Under the illuminating light, these lines will be clearly seen, so make sure your aquarium light is on.

Step 5 Distinguishing The Sex Of Glofish Tetra With Body Structure

Now, it is time to look at the physical size and shape of your beloved Glofish Tetra. This is another factor that will help you to differentiate male glofish tetra from female ones.

Male GloFish tetras are slightly smaller than female Glofish tetra. So, if you see this difference, you can easily point out the male ones.

Also, male glofish are slightly slender in width as well as will seem a little petite than females. Hence, all you have to do is observe.

Why Is Determining The Sex Of Glofish Tetra Important?

Okay, now we have made it through the determination step, it is time to know its importance. And I know you are wondering why people often tell you to know the gender of your glofish tetra.

The GloFish Fluorescent Fish License strictly states, “Intentional breeding and/or any sale, barter, or trade, of any offspring of GloFish fluorescent ornamental fish, is strictly prohibited.”

Hence, anything illegal can be scary, and no one really wants to cross the law, and I hope neither do you.

See, here is the problem when you don’t know the sex of the glofish tetra you are petting in the tank, you might end up having fry in the tank.

Breeding and spawning are natural phenomena if there are two different sex glofish tetras present in the tank.

And, you can’t control the natural process like breeding GloFish when you don’t know their gender. Learn more about Breeding GloFish Tetra.

Seeing a fry all of a sudden in the tank can be scary. It will cause a dent in your wallet while caring for them.

You can’t sell them to the pet store or the local buyer, hence a few more glofish tetra to care for.

Not that having a tank full of glofish is bad, but your budget needs to broaden, too, as you have a few more fish to care for.

If you have an idea about their gender, you can take the necessary steps to overcome the breeding problem or can be mentally prepared for the new fry you will see in the tank.

Frequently Asked Questions

Here are answers to the few FAQs about Glofish you might be wondering about as well.

Can Glofish Tetra Have Babies?

Yes, Glofish tetra can lay eggs that male glofish tetra will fertilize, and you will see fry after a few days of fertilization.

But if you have the query if these tetras are livebearers or not, then the answer is no. These Glofish lay eggs and are not livebearers.

But yes, they are very fertile, although some aquarium enthusiasts argue otherwise, and can reproduce new glofish tetra.

Do Glofish Lay Eggs?

Yes, Glofish lays eggs when male and female glofish mates are in the tank during a breeding season. Apparently, you will see female glofish laying eggs every two to three days, and each clutch contains hundreds of eggs.

I have also written an article on How Often Do Glofish Lay Eggs? Have a look!!!


In conclusion, curiosity and responsibility make people do wonders, and hence raising a question about glofish tetra sex is a simple example of it. If you are a good observer with keen sight, you will be able to distinguish your glofish tetra gender easily. You will be fine if you follow the steps and instructions carefully.

If you have any more queries, drop a comment in the comment box below, I am here to help.

Good Luck!

Happy Fish Keeping!!!

Recommended Articles:

  1. How to Set Up Tank for GloFish: Beginner’s Guide
  2. Do Glofish Need Heater In Their Tank

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