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What Are GloFish? Everything You Need to Know

GloFish are known for their vibrant colors and fascinating glow. These are genetically modified fish that were created by adding genes from jellyfish and sea-coral. They offer a unique and colorful addition to fish tanks.

Although they look different then their non-genetically modified counterparts, they have lots of similarities and attributes. Let’s dive deeper into the world of GloFish and explore what they are in detail.

Types of GloFish

They are available in several types, each with its own unique color and species characteristics:

  • GloFish Danio: These are active and hardy fish, known for their striking stripes and bright colors like neon green and fiery red.
  • GloFish Tetra: With a more rounded body, these fish glow in shades of pink, orange, and blue, creating a mesmerizing effect.
  • GloFish Barbs: Known for their speed and playful nature, GloFish Barbs come in electric colors such as yellow and purple.

Each of these types adds a distinctive flair to aquariums, appealing to fish enthusiasts of all ages.

Are GloFish Natural?

Glofish in tank
GloFish Swimming on Tank. Picture taken by Fish Affordable

No, GloFish’s are not natural in the traditional sense. They are genetically modified organisms (GMOs).

These GMO fish were created by introducing foreign genes into the genome of the fish that make them fluoresce in various colors under certain types of light. 

Their genetic modification process does not occur naturally. It involves the deliberate alteration of the genetic makeup of the fish in a laboratory setting.

The introduced genes typically come from other organisms, such as jellyfish or sea coral, which naturally produce fluorescent proteins. For example, the green fluorescent protein (GFP) gene is originally found in jellyfish. It was one of the first genes used to create GloFish.

Therefore, while they are based on species that exist in nature, such as the zebrafish (Danio rerio), their unique fluorescent colors are the result of human-engineered genetic modifications and are not found in wild populations of these species.

This process, which is safe for the fish, gives them their signature glow. The modification is inheritable, meaning the bright colors pass down to their offspring.

Where did GloFish Come From?

In 1999, Dr. Zhiyuan Gong and his team at the National University of Singapore actively developed the first Glofish, a type of fluorescent zebrafish (Danio rerio).

They worked with a gene from a jellyfish that makes green fluorescent protein (GFP) and actively inserted it into a zebrafish embryo. It caused the fish to brightly fluoresce under both natural white light and ultraviolet light. Their primary goal was to create a fish that would detect pollution by glowing in the presence of environmental toxins.

Yorktown Technologies, a company based in Austin, Texas, later acquired the worldwide rights to market these fluorescent zebrafish, branding them as “GloFish.” They were introduced to the United States market in late 2003.

How Long do GloFish Live?

On average, GloFish has a lifespan of up to 5 years. Since these fish are genetically modified versions of existing fish species like zebrafish, black tetras, tiger barbs, and others, their lifespan is likely similar to the unmodified versions of these species.

For instance, zebrafish, which were the first species used for creating GloFish, typically have a lifespan of around 3 to 5 years in captivity, assuming they are kept in ideal conditions.

The lifespan of other species used for these fluorescent fish, like black tetras, tiger barbs, and rainbow sharks, can vary but generally falls within a similar range, depending on the species and the quality of their care.

To ensure a longer lifespan, it is important to maintain proper tank conditions, including clean water, appropriate temperature, and a suitable diet, as these factors play a significant role in the health and longevity of aquarium fish.

How Big do GloFish Get?

GloFish are relatively small, with most species growing to an average size of 1.5 to 3 inches. The size varies depending on the species of fish they are genetically modified from. They are available in several species, each with its own average adult size:

  • Zebrafish (Danio rerio): The original GloFish, zebrafish typically grow to about 2.5 to 3 inches (6.4 to 7.6 cm) in length.
  • Black Tetra (Gymnocorymbus ternetzi): Also known as the skirt tetra, these fish can grow up to about 2 inches (5 cm) in length.
  • Tiger Barb (Puntius tetrazona): Tiger barbs can grow to be about 3 inches (7.6 cm) long.
  • Rainbow Shark (Epalzeorhynchos frenatum): Despite the name, these are not true sharks. They can grow up to about 6 inches (15 cm) in length.
  • Siamese Fighting Fish (Betta splendens): These fish, often simply called bettas, typically grow to about 2.5 to 3 inches (6.4 to 7.6 cm) long.
  • Bronze Corydoras (Corydoras aeneus): These are smaller fish, usually reaching about 2.5 inches (6.4 cm) in length.

The size of the fish in your aquarium will depend on which species you choose. It’s important to consider the adult size of these fish when setting up an aquarium to ensure they have enough space to thrive.

Can GloFish Live with Goldfish?

While it is tempting to have GloFish with goldfish, their fundamental differences in habitat needs, temperature requirements, and behavior make it challenging and potentially harmful to house them together.

So, No. I’d not recommend putting them in the same tank.

GloFish are tropical fish. So, they require warmer water temperatures. On the other hand goldfish are cold-water fish.

Also, goldfish produce a significant amount of waste. It leads to poor water conditions for sensitive species like GloFish.

Can GloFish Live with Tiger Barbs?

GloFish can coexist with tiger barbs under the right conditions, as both species have similar water requirements. Both GloFish (specifically the Tiger Barb variant) and Tiger Barbs are very active and have aggressive behavior.

They are schooling fish and are best kept in groups. Since they share similar water parameters and tank environment requirements, it’s possible to keep them together. However, you should always keep an eye on them as they have fin-nipping behavior.

You might also like: Do Tiger Barbs Bite?

Can GloFish Have Babies?

Yes, GloFish can have babies. Their reproductive process is similar to their non-genetically modified counterparts. However, These fish are created and distributed under specific licenses, and unauthorized breeding and distribution are prohibited.

Here are some requirements for them to breed:

  • Breeding Environment: To encourage breeding, the aquarium conditions need to be optimal. This includes maintaining appropriate water temperature, pH levels, and providing a diet rich in nutrients.
  • Spawning: The specific breeding behavior depends on the species of GloFish. For example, zebra danios scatter their eggs, while tetras may lay eggs on plants.
  • Fertilization: Males have to fertilize the eggs once they are laid.
  • Incubation: If the fertilization is successful, the eggs will hatch after a period of incubation, which varies by species.
  • Caring for the Fry: The newborn fish, or fry, usually requires special care with appropriate food and water conditions to ensure their survival and growth.

If you are considering breeding GloFish, it’s crucial to do thorough research specific to the species you have and ensure you are in compliance with any legal guidelines.

Do GloFish Lose Their Color?

GloFish typically don’t lose their color during their lifetime. They maintain their vibrant fluorescent colors throughout their relatively short lifespan. However, certain factors can cause them to lose their color.

Factors that make GloFish lose their colors:

Stress and Lack of Nutrition: Stress is a primary reason for GloFish losing their color. It can be due to various factors including poor water quality, aggressive tankmates, overcrowding, or improper nutrition. A balanced diet with foods like brine shrimp, bloodworms, and daphnia can enhance their nutrition and help maintain their color.

Tank Conditions and Companionship: Overcrowded or small tanks lead to stress and color loss. A minimum of 20 gallons is recommended for 6-8 fish. It’s also important to have company.

Water Quality and Temperature: Good water quality and oxygenation are crucial to maintain their color. The tank should have good airflow. The water temperature should be maintained between 72-82°F. Ammonia and nitrite spikes can lead to discoloration.

To enhance their radiating color, consider using black lights (UV lights) which can make their colors pop more vibrantly. Additionally, provide a diet high in carotenoids and maintain a clean tank with regular water changes.


GloFish are an exciting addition to the aquarium hobby. They offer a unique visual experience and an opportunity to learn about genetic science. While their care needs are somewhat similar to other tropical fish, their vibrant colors and the ethical considerations surrounding their creation set them apart. For those looking to add a splash of color to their home aquarium, the vibrant creatures can be a delightful choice.

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