How To Tell If Your Glofish Tetra Is Pregnant?

Glofish tetra is pregnant

Glofish might be man-made genetically engineered fish but boy, it is pretty, isn’t it? And if you are wondering about the baby glofish, then let me tell you how beautiful they look while growing. Although an illegal word is attached to breeding glofish, how can someone win over nature? You can’t change the inevitable if you have male and female glofish tetra in the tank. Female tetra is bound to get pregnant when they hit sexual maturity and are in the presence of male glofish tetra. But how to tell if your glofish tetra is pregnant?

Curved belly to swollen bellies is what gives the pregnancy in Glofish tetra away. Although it is hard to tell males and females apart, it will be quite evident when the female glofish tetra gets pregnant. After a few days, you will find small jelly-like eggs in the tank.

This is just a layer of information on the egg layers glofish tetra; let’s dive into the depth of the pregnancy in glofish.

In this article, I will help you to understand the what, the how, the when, and the why related to the pregnant glofish tetra.

How to Tell if your Glofish Tetra is Pregnant?

First of all, Glofish tetras, like any other tetras, are egg layers. So technically they can’t get pregnant. Livebearers like guppies, mollies, etc., can actually get pregnant.

Did you know that there are different ways in which fish reproduce? Livebearers like the egg-carrying glofish tetra fertilize the egg inside the female’s body, while egg layers only carry the egg.

Now, while it’s not technically correct to call the egg-carrying phase “pregnancy,” we can use that term for simplicity’s sake.

So, if you’re wondering whether your glofish tetra is pregnant or not, here’s a tip: look for a swollen belly! That’s a sign that there are eggs developing inside, ready to be fertilized externally by a male glofish tetra.

Differentiate The Gender

Okay, hands down, this is the hardest step of all. Glofish tetras show no sexual dimorphism until adulthood. So it is nearly impossible to differentiate the gender.

Let me help you here, although it is not that easy. This advice will help you to some extent. Wait till they reach their sexual maturity.

You can’t differentiate the sex of glofish tetra beforehand. So, when they hit maturity, i.e., 4 to 6 months after their birth, follow the instructions and look for the signs I will point out below for you:

  1. Illuminate the tank with glofish tetras with GloFish Cycle Light From Tetra or All Glass Aquarium Fluorescent Strip Light.
  2. Clean the tank so you can clearly see the glofish tetras.
  3. Look for the secondary line along the blue strip, which is the primary line.
  4. If the second line is golden, then the glofish tetra you are looking at is male.
  5. And, if the second strip is silver, then that’s your female glofish tetra.
  6. Furthermore, look at the shape and size of those glofish tetras.
  7. Females usually have a rounded, pot-bellied look, whereas the male glofish tetras are slimmer.

You might like to read a full article on the Sex Of GloFish Tetra: How To Tell If Your Glofish Tetra Is Male Or Female?

Swollen Belly

When you know which of your glofish tetras is female, look closely at them to see if they have a rounder belly.

Although it is their signature feature to have a round belly, the belly grows slightly while she is carrying eggs.

So, compare the before and after size of glofish tetras, especially those females, to be quite certain about the pregnancy.

Courting Behavior

Once the female glofish hits sexual maturity, she releases pheromones to begin the courting or spawning behavior.

Consequently, the male glofish tetra then releases gonadal pheromones to cause ovulation in the female glofish tetra.

If you see the male glofish tetra chasing the female ones, understand that they are pursuing her to lays eggs.

After a few days of all this, you will see tiny jelly-like clutches of eggs in the bottom of the tank.

Is The Glofish Tetra Just Fat Or Pregnant?

People often mistake overweight and obesity as pregnancy in these glofish tetras, so there is the slightest chance that your tetra is just overweight, not pregnant.

Overfeeding, the very trait of tetra, is also present in the genetically engineered glofish tetra. Well, they could not change that, do they?

Along with many traits, overfeeding, the love for food, and not knowing when to stop eating are probably still in your glofish.

Try researching the accurate diet for your glofish tetra and follow the instructions there. You’ll get your answer if they lose weight within a few days.

Also, the water parameters play a huge role in bloating fish or making fish fat. You can try to test the water and maintain the ideal parameters as soon as possible.

Is The Glofish Tetra Sick Or Pregnant?

Another reason for the swollen tummy of glofish tetra can be because they are sick. There are many diseases that clearly show swollen bellies as one of their symptoms.

People often confuse it with pregnancy in glofish; however, their glofish is actually dying.

Poor water quality with high ammonia content and high level of nitrite can bring so many diseases to Tetras, including dropsy. Learn more about Tetra Fish Diseases and Treatments.

When triggered by these factors, dropsy shows its symptom of a swollen belly first, which is then mistaken as pregnancy in glofish.

There is no cure for dropsy, but not contagious to other fish in the tank, so there is your silver lining.

Also, make sure the water parameters are ideal and accurate, and try changing the water before the case gets out of hand.

Look closely at both male and female glofish. If both of them show symptom, you are in trouble.

Or else, test the water, and if the water parameters are okay and only the female glofish tetra has swollen belly, then it might be pregnant.

Prepare to take care of the eggs and fry of glofish tetra.

Things To Do When Your Glofish Tetra Is Pregnant

Once you are sure about the eggs in the female glofish tetra, you have to provide the necessary things to ensure their safety.

You can get a nice descriptive article on this here!

Let me point out some major things to look at when your glofish tetra is carrying eggs:

Filtration Of The Breeding Tank And The Aquarium Nitrogen Cycle

Although the breeding of glofish tetra is unintentional, you need to ensure they are getting everything appropriate when the female carries eggs.

Filtration and the aquarium nitrogen cycle are two important factors that decide the survival of pregnant glofish tetra and their eggs.

Clean water with no presence of ammonia and nitrite is what these tetras ask for in the tank. Learn more about How to Clean a Tetra Fish Tank? [Step-by-Step].

Glofish tetras are weak and vulnerable when they are carrying eggs, like any other living being.

The slightest change and carelessness can become the death of female glofish along with the eggs inside them.

You might like to read a full article on Types of Aquarium Filter For Tetra Fish and Filtration Methods.

Heater In The Breeding Tank

In the breeding tank or, say, the tank where glofish are supposed to lay eggs, the temperature needs to be 78°F.

Temperature plays quite an important role in the survival of tetra, be it glofish or any other tetra.

And the pregnancy phase can be tiring and weakening. So temperature change can bring diseases and problems in the glofish.

Aqueon Pro 100 Submersible Aquarium Heater will be ideal for your tank with glofish. You can easily find and order this heater on and from amazon, respectively.

Diet For The Glofish Tetra

The nutritional value of the food you feed your glofish tetra must be accurate to the nutrients their body asks for.

You can’t compromise the health of these tetras by feeding them less or inappropriately. With healthy and nutritional diets, your glofish will lay eggs, and the fry developing from them will be healthy too.

Tubifex to frozen brine shrimps along with the commercial flakes, you can make a proper diet plan for these tetras.

How Often Do Glofish Tetra Lay Eggs?

Well, during the breeding season, which is the rainy season for most tetras, glofish tetras are quite active sexually.

So, there is a high probability of seeing many clutches of eggs within the interval of a few days.

The female glofish tetras, when it hits maturity, have the capacity to lays eggs every two to three days.

Thus, by the end of the rainy season, you will find hundreds of eggs in the tank along with the fry.

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

How Many Eggs Do Glofish Tetra Lay At Once?

I mentioned in the above section the frequency of egg-laying in female glofish tetra. But it is equally important to know how many eggs you should be expecting each time they lay eggs.

This will make it easier for you to prepare yourself mentally while making the preparations for new baby tetras to arrive.

When a female glofish tetra releases the eggs, you will see a clutch of several hundred eggs each time.

If only all of them fertilized, hatched, and developed into new glofish tetras, it would be a nightmare for you.

What Do Glofish Tetra Eggs Look Like In A Tank?

When you see your male glofish tetra following and chasing your female glofish tetra, be ready to see eggs in the tank.

But what should you look for? Are their eggs colorful like their body? Sorry to say, but eggs will have no such color, and it will be quite hard to pinpoint the location of eggs.

The glofish tetra’s eggs are transparent and are white or slightly yellow. These eggs look like tiny cream or whitish orbs in the tank. However, it can be hard to see unless you are attentive and observant enough or it will be easier if you have a black substrate in the tank.

These eggs seem to be in a clutch together and are most often eaten by parents glofish. You need to take correct precautionary measures to save the egg before they hatch. Furthermore, you need to keep Java moss as it helps you to identify eggs easily. These eggs look like a tiny grains of sand lying on the Java moss.

You can buy Java Moss Portion in 4 Oz Cup – Easy Live Fresh Water Aquarium Plants from amazon.

How Long Does It Take For Glofish Eggs To Hatch?

After the female lays the eggs, the male glofish tetra fertilizes it immediately. Once the egg is fertilized, you will see a black dot inside it.

The black dot in the egg suggests successful fertilization, whereas its absence suggests unfertilized eggs.

After all this, you have to wait for these eggs to hatch for a few days, 2 to 3 days, to be precise.

But the fry will take some time to come out of hiding, so wait for a few more days to see new babies of glofish tetra.

You need to make sure the tetra fry tank is well-filtered and clean with no presence of ammonia or nitrite.

Here is an article to guide you about Aquarium Filters Best Suited For Tetra Fish Fry

Frequently Asked Questions

You might have a few more questions lingering in your mind, so let me help you. Here are answers to a few FAQs on glofish tetra that might help you.

Is Glofish Fertile?

Yes, Glofish is Fertile. Although there is a huge war on this topic, some aquarium enthusiasts highly speculate that the glofish are supposedly made infertile.

However, this is not the case, as glofish are no doubt fertile and can lay eggs when the female mates with a male glofish.

Even in the captive situation, if both male and female are present, there is a chance of seeing eggs as well as fry in the tank sooner or later.

Is It Illegal To Breed Glofish?

Yes, it is illegal to intentionally breed, barter, or trade glofish tetra as the license and copyright to do that legally belong to the GloFish Company.

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.”

Glofish is a patent breed; hence, the company covers the selling and reproducing of any glofish.

You will be punished according to the law if you are found breeding or selling these fish intentionally.


Glofish tetras might be illegal to breed, but you have no say in the natural phenomenon. Even if you want to stop breeding and spawning, you will have a hard time separating males from females. And when there are two genders of glofish tetras present in the tank, it is quite impossible to stop the female from laying eggs or the male from fertilizing them.

All you can do is contemplate whether your glofish are pregnant and act accordingly. Try to give a favorable environment for the development of new baby glofish tetras. But never try to sell them to the pet store or the local fishkeeper: it is illegal.

Although ‘the more, the merrier’ here, it can be a nightmare caring for so many glofish tetras at once. You know, neither all the eggs nor the fertilized eggs hatch is fertilized. So, the minimal survival rate of eggs and fry makes it easier to prepare for fewer new ones.

You will do a good job until and unless you follow my instructions. And if there is something you want to ask, remember I am just a comment away.

Recommended Articles:

  1. Breeding Tetra Fish – Step By Step Guide
  2. Tetra Fry Tank Set-Up: Fish Tank Requirement For The Fry
  3. How to Set Up Tank for GloFish: Beginner’s Guide
  4. How To Feed Tetra Fish Fry Properly | Dos & Don’ts With Alternative Food


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