Can Glofish Get Pregnant?

Glofish have become a popular addition to aquariums around the world. These genetically modified neon fish come in a wide range of colors and are adapted from existing breeds of aquarium favorites. Because of this, caring for and in turn, breeding Glofish is no different than caring for the breed from which they are derived.

A glofish cannot get pregnant. One of the physical characteristics of female Glofish is a rounded, pot-belly. This may lead owners to believe that their Glofish is pregnant, but Glofish are egg carriers and do not give birth to live young. Instead, they carry eggs in their bellies from maturation age, which, when kept with a male Glofish, can become fertilized.

Glofish are a beautiful ornamental addition to any aquarium, and the inclination to breed them and create more of these visually stunning fish is understandable. Glofish are considered a patented product and do not exist in the natural world, so there are some essential things to keep in mind if you are considering breeding your Glofish.

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The Female Glofish Releases Eggs For Fertilization

The most popular and easiest to breed Glofish are the Glofish Danios. The female Glofish at maturity is larger than the male and carries her eggs in her belly. Over time, she may become laden with many eggs, which contributes to her very “pregnant” appearance.

Glofish Danios mate best in groups, and you will want to have more than one male and multiple female Glofish. A female Glofish will only release eggs for fertilization if there are male Glofish present. Once a female Glofish releases her eggs, male Glofish will swim by and fertilize them.

How to Spot Glowfish Eggs

The eggs then sink to the bottom of the tank and fry usually hatch within 2-3 days, but you likely won’t see the newly hatched babies swimming around for another three days or so.

Like most fish, it is a common occurrence for the adults to eat the released eggs before they have an opportunity to hatch. Because of this, when attempting to breed Glofish, you must keep a watchful eye on your tank at all times and immediately remove the adult fish once the eggs have been spawned and fertilized.

Remember that the survival rate for fertilized eggs is very minimal, so it will likely take many attempts before you find yourself with Glofish fry to care for.

Glofish Breeding Requires Both Male and Female Glofish

The most important thing to keep in mind if you are planning to try breeding your Glofish is that the company that produces them owns both the license and the trademark. This means that if you plan to breed your Glofish intentionally, and can produce fry, you cannot under any circumstance, sell or distribute them.

Some general and important facts when breeding Glofish:

  1. You cannot interbreed the different species of Glofish.
  2. Care and breeding of your Glofish are identical to that of your species’ natural counterpart.
  3. Two Glofish of the same color will produce an identical colored offspring. When mixing Glofish colors, the resulting fry will consist of half of one of the colors and half of the other.
  4. It is likely that the further out the generations go, the fluorescence and vibrancy can diminish.

There Are Ways To Increase The Chances of Successful Glofish Breeding

When preparing your Glofish and tank for breeding, there are some things you can do to help ensure success.

  1. Make sure your Glofish are being fed the right diet. High-quality foods are essential to healthy breeding.
  2. Use marbles or larger gravel as your substrate. These materials allow for small spaces where fertilized eggs can slip into and be protected against being eaten.
  3. Keep an eye out for typical breeding behavior. Generally, Glofish that are ready to breed will start swimming after each other just before the female is set to drop her eggs.
  4. Check your tank frequently for signs of fertilized eggs. After noticing indicators of breeding, it’s good practice to remove your adult Glofish and check your tank and substrate for fertilized eggs.
  5. Allow 3-5 days for any new fry to be hatched and begin swimming out and around your tank.
  6. All Glofish that are bred must stay in your possession as it is illegal to sell, trade, or distribute Glofish.

Glofish Are Illegal in California

Glofish are currently only available in the United States. There are currently no regulatory measures taken over the technology that produces these permanently luminescent fish. However, they are banned and illegal in California.

The Fish and Game Commission of California ruled in 2003 that the creation of Glofish was a “trivial use for a powerful technology.” (Source:

Where Did Glofish Come From?

Glofish were first introduced in 2003 by Yorktown Technologies. They are a fully patented, particular brand of fluorescent fish. Glofish are created using a technology that used the study of bioluminescence to genetically modify a breed of fish to maintain a constant glow. Bioluminescence is most easily understood by the example of the lightning bug.

Two chemicals must be present within a living organism to allow for its ability to glow or fluoresce. The study of these chemicals has allowed for scientists and researchers to create adapted genes built to provide a species with a constant glow.

While some fluorescent or neon aquarium fish have been altered through the injection of dyes and other artificial enhancements, it is important to note that the Glofish brand are genetically modified fish, and so, produce their fluorescence “naturally.”

The particular gene that lends its lighting power comes from a jellyfish. To engineer Glofish, technicians carefully inject this gene into the developing embryo of particular species of fish, resulting in the birth of a fully fluorescent version of the same species.

Because Glofish are created by the introduction of a specialized gene, all Glofish are created from existing species of aquarium fish. The most common Glofish breeds are:

  • Danios: The first Glofish released to the public was the Starfire Red Danio. Sometimes called a Zebra fish, Glofish Danios come in a variety of colors and are the most common and most popular Glofish species.
  • Barbs
  • Tetras
  • Bettas

The Glofish brand offers six engineered and patented color options for all of its species of Glofish. Glofish are available in:

  1. Starfire Red®
  2. Electric Green®
  3. Sunburst Orange®
  4. Cosmic Blue®
  5. Galactic Purple®
  6. Moonrise Pink®

How to See Your Glofish Glow in The Dark

Glofish are a beautiful addition to any freshwater aquarium and are easy to care for. To see and fully appreciate their “glowing” capabilities, your tank will require specialty lighting.  In natural and white light, your Glofish will appear bright and vibrant. The use of blacklights is essential for your Glofish to deliver its signature fluorescent neon hue.

One of the most interesting things about the way the Glofish’s bioluminescence works is that the fish itself isn’t truly “glowing.” In fact, the gene they carry from the jellyfish allows them to absorb light and then re-emit it.

This gene is what will inherently be passed down to the offspring of your Glofish when they reproduce. Breeding Glofish may not always be easy or successful, but it can be a fun way to add more of these fantastic, brilliant colored fish varieties to your aquariums.

If you are noticing that your female Glofish are starting to take on a full-bellied, pregnant look, then she definitely has potentially viable eggs, that with a little patience, and the help of her male counterpart, can produce the next generation of these beautiful fish.