GloFish: Unlocking the Secrets to Successful Care

Last time I was in a local pet shop some new, bright fish caught my eye. I recognized their body shape, but the colors…I don’t belong to those who support the idea of genetic modification of fishes, but in this case the fish really deserves to be spoken about. So, let me introduce you a GloFish!

The story of creation

As you may guess, such fish can not be encountered in the wild. GloFish — is a patented commercial brand that sells genetically modified fluorescent tank fishes. The name contains two words: glow and fish. This is the name of the brand that sells transgenic fishes in the USA, but Taikong Corp in Taiwan is considered to be the official breeder of these fishes.

How are glofish made?

The fishes were genetically modified to obtain this bright neon glow. Gene of one of Pacific jellyfish species was put into the fish DNA to ensure synthesis of green fluorescent protein to make the fish glow. This is how GloFish appeared!

The first fish to get this gene was zebrafish (Danio rerio) — these are not demanding and popular cyprinoid tank fishes. These transgenic fishes differ from their initial form with their body coloring.

The fish DNA contains DNA of a jellyfish (Aequorea Victoria) and red coral (from Discosoma genus).

Zebrafish with jellyfish DNA paragraph (GFP gene) are green colored, with the coral DNA (RFP gene) — they are red, and the fishes with DNA paragraphs of both the jellyfish and the coral are yellow colored. Due to these foreign proteins the fish glow brightly in UV light.

Initially the experiments had scientific purpose: the fishes had to act as indicators of water pollution, i.e. when there are some dangerous toxic substances in the water the fish should change its color.

During one of scientific conferences the picture of transgenic fish was shown to the public and it appeared to be very interesting to representative of a company that was selling tank fishes. As a result, the scientists got the job to create another fluorescent species. Scientific and business collaboration has led to signing the agreement and appearance of a new brand GloFish, that is now selling different kinds of fluorescent fishes.

What makes glofish glow?

The specific gene responsible for the glow in GloFish is derived from a sea anemone and encodes a protein called green fluorescent protein (GFP). When this gene is activated in the cells of the fish, it causes them to produce GFP, which emits light when exposed to certain wavelengths.

The introduced genes are incorporated into the fish’s genetic makeup, and as a result, the fish’s skin, scales, and sometimes even their internal organs can emit a fluorescent or glowing coloration under specific lighting conditions. By using specialized LED lights that emit specific wavelengths, such as blue or ultraviolet light, the fluorescent proteins in the GloFish can be excited, causing them to emit their characteristic glow.

Types of glofish

It’s important to note that while GloFish exhibit this unique fluorescence, their genetic modification does not alter their basic care requirements or behavior compared to their non-modified counterparts. All species have fluorescent coloring once they are born and it remains through the whole life of the fish and becomes brighter as the fish grows. This fluorescent coloring is transferred to their offspring when breeding of transgenic species.

In 2012 a new a new species of fluorescent tank fish appeared, it was named «Electric Green» GloFish. This fish was bred the same way as the previous ones, but instead zebrafish they used black tetra (Gymnocorymbus ternetzi).

In 2015 tiger barb (Puntius tetrazona) glowing with green was introduced on the market. Only a short time ago glo-Rainbow Shark (Epalzeorhynchos frenatum) appeared on sale.

GloFish tetra

starfire red tetra

The scientific name of GloFish tetra is Gymnocorymbus ternetzi. It is the same scientific name as the regular tetra, as GloFish tetras are genetically modified versions of the black skirt tetra species.

In 2012 the same company executed an order to create fluorescent black tetra. Thus, due to joint efforts of scientists and business decorative aquarium husbandry has obtained unique species that allow to create completely new glowing tank design. Except their fluorescent glow transgenic fishes don’t differ much from their initial natural forms. Their size, lifespan, behavior and diet are almost the same, but they have some nuances. Even their lifespan doesn’t differ from this of ordinary black tetra – it equals to 3-5 years.

For example, they don’t have any visual gender dimorphism, since both males and females have the same coloring. The only difference they have is that female have more rounded abdomen.

Glowing coloring of tetra will not change or disappear – it is put in their genetic pattern and it will be transferred to their offspring. To see how the fish glows it’s better to provide them with blue lighting. The coloring will be bright at white (ordinary) lighting, but not as bright as it could be. Due to glowing tetra brightness and unpretentiousness it is easy to keep them even for beginning aquarists.

GloFish tetras are fluorescent and exhibit their brightest colors under blue light. Consider using a blue LED light or a GloFish-specific light to enhance their vibrant appearance.


Here are some common behaviors of GloFish tetras:

  1. Schooling: GloFish tetras are schooling fish, which means they feel more secure and comfortable when kept in groups of six or more. They tend to swim together in a coordinated manner, displaying schooling behavior.
  2. Active Swimming: GloFish tetras are active swimmers and enjoy exploring their environment. They will often dart and swim swiftly throughout the tank, especially when they feel safe and secure in a well-planted tank.
  3. Peaceful Nature: GloFish tetras are generally peaceful and non-aggressive towards other fish species. However, occasional chasing or fin nipping can occur within their own species, particularly if the group is too small or if there is a lack of hiding spots.
  4. Mid to Top Water Swimmers: GloFish tetras tend to occupy the middle to upper levels of the aquarium. They are not bottom-dwelling fish and will spend most of their time in the mid to top regions of the water column.
  5. Color Changes: The fluorescent colors of GloFish tetras can change in response to their environment, stress levels, and lighting conditions. They may appear more vibrant and intense under blue lighting.
  6. Timidness: While GloFish tetras are active swimmers, they can also be slightly timid and skittish, especially when introduced to a new environment. Providing adequate hiding spots and a well-planted tank can help them feel more secure.


GloFish tetra is the same enduring as a common black tetra. The fish is perfect for community tanks, though they may become less active if not kept in groups large enough.

Provide a suitable aquarium with a minimum size of 10 gallons, though it’s better to choose not very deep elongated volume with a cover. A larger tank will allow for a more stable environment and provide more swimming space for the fish. Glofish tetra feels more comfortable and behave better in groups of 6-8 fish and more. This is an active fish that swims in medium and low tank water layers. Tank plants should leave some open spaces for the fish to swim.

The glofish tetra is not demanding to tank parameters. The ideal water temperature for GloFish tetras is between 72-78°F (22-25.5°C). The pH level should be kept around neutral, between 6.5 and 7.5. Regular water testing and water changes are important to ensure good water quality.

Install a reliable filter to maintain water quality by removing debris and providing water circulation. Additionally, consider using an air pump or aquarium airstone for proper aeration.

Perform regular tank maintenance, including partial water changes (about 25% every 1-2 weeks), cleaning the substrate, and maintaining the filtration system.


How big do glofish tetras get?

GloFish tetras, have the same size as regular black tetra, as they are genetically modified versions of the species. Adult GloFish tetras typically reach a size of around 2.5 to 3 inches (6 to 8 centimeters) in length. Males tend to be slightly smaller and more slender compared to females. 


The average lifespan of GloFish tetras is typically around 3 to 5 years. However, with proper care, some individuals may live slightly longer, reaching up to 5 to 7 years. Various factors can influence the lifespan of GloFish tetras, including water quality, diet, genetics, and overall tank conditions. Providing a well-maintained and suitable environment, along with a balanced diet and regular monitoring of water parameters, can help promote the longevity and well-being of your GloFish tetras.


You can feed them with various food: flakes, small pellets and frozen food (daphnia, brine shrimp, cyclops, blood worm etc.). Offer a balanced diet consisting of high-quality flake or pellet food formulated specifically for tropical fish. Supplement their diet with occasional live or frozen foods like brine shrimp or bloodworms. Feed them small portions multiple times a day, and ensure they consume the food within a few minutes.

Tank mates

GloFish tetras are peaceful fish that can coexist well with a variety of tank mates. Here are some suitable tank mates for GloFish tetras:

Glofish tetra male vs female

Determining the sex of GloFish tetras (Danio rerio) can be a bit challenging as they do not display pronounced physical differences between males and females. However, there are a few subtle characteristics that can help differentiate them:

  1. Body Shape: In some cases, female GloFish tetras may have a slightly rounder belly compared to males, especially when they are carrying eggs.
  2. Coloration: While there are no distinct color differences between male and female GloFish tetras, during breeding or when females are carrying eggs, they may appear slightly fuller or more vibrant in color.
  3. Behavior: During breeding, males tend to display more intense colors and may exhibit courtship behavior, chasing females and making jerking movements to entice them to spawn.

It’s important to note that without close examination or observing specific breeding behaviors, it can be challenging to determine the sex of individual GloFish tetras. The best way to ensure a balanced population is to keep a group of tetras in a ratio of multiple females to males. This can help create a harmonious environment and reduce the chances of excessive aggression or stress.

Common NamesGlofish Tetra
OriginOriginally found in India, but bred selectively for color
Size1.5 to 2 inches (3.8 to 5 cm) in length
Lifespan2 to 3 years
Water ParametersTemperature: 72-82°F (22-28°C), pH: 6.5-7.5
BehaviorActive and schooling fish
Color VariationsFluorescent and brightly colored (red, green, orange, etc.)
DietOmnivorous; eats both live and commercial fish food
Tank SizeMinimum 10 gallons (37 liters) for a small school
Tank SetupWell-planted tank with hiding places, open swimming areas
CompatibilityPeaceful and compatible with other small, non-aggressive fish
BreedingEgg-scatterers; breeding can be challenging
Special ConsiderationsMay require special lighting for optimal color display

GloFish barb

Due to the genetic scientists work a picturesque GloFish barb appeared in 2012. It was bright green yellow with barely seen vertical stripes and fins with red edges.

In 2015 a new «high-contrast» barb with black stripes and black fins appeared and the red one appeared a bit later. Except their fluorescent glow the fish doesn’t differ much from its natural original species. Their size, lifespan, behavior and diet is almost the same.

They are not demanding as for tank parameters, but it’s better to choose not very deep elongated volume with a cover. Tank plants should leave some open space for the fish to swim.

GloFish barb is the same enduring as a common tiger barb. This is an active fish that swims in medium and low tank water layers.

The glofish barb is perfect for community tanks, though they may become less active if not kept in groups that are large enough. Tiger barb feels more comfortable and behave better in groups of 6-8 fish and more.

The diet can consist of various food: flakes, small pellets and frozen food (daphnia, brine shrimp, cyclops, blood worm etc.).

Scientific NamePuntius tetrazona
Common NamesGlofish barb
Range and habitatAsia
Sizeup to 10 centimeters (3.9 inches)
Lifespan3 years
Ease of keepingMedium
Minimum tank size50 liters (11 gallons) and more
TemperamentSometimes aggressive
Temperature21–27 °C (70–81 °F)
Water hardness5-20 dGH

Glofish danio

Danio rerio is the first pet that was genetically modified with dioluminescence genes in 2003. Though initially the fish was bred not as a decorative one, it became the first generally available genetically modified pet.

GloFish — is a patented commercial brand name that is used to sell genetically modified fluorescent fishes; the first one here was danio rerio. The main distinctive feature of glofish species that were artificially bred by means of genetic modification from their initial form is its red, green or orange fluorescent coloring, that becomes more visible and intense at UV light.

Transgenic fidh differ from their initial species by the body coloring. The DNA has DNA paragraphs of a jellyfish (Aequorea Victoria) and a red coral (from Discosoma kind). Danio with a jellyfish DNA paragraph (GFP gene) have green coloring, with the coral DNA paragraph (RFP gene) — it is red; fishes that have both DNA paragraphs in their genotype are yellow colored.

In addition to red fluorescent danio rerio that is sold under the trademark Starfire Red, green and orange-yellow fidh were bred in the middle of 2006; in 2011 blue and violet colored species followed them.

These genetic lines got trademark names Electric Green glofish danio, Sunburst Orange glofish danio, Cosmic Blue glofish danio and Galactic Purple glofish danio. All these fishes were bred using genetic engineering by means of recombinant DNA taken from various sea corals. Unlike artificially colored fishes glofish preserves its coloring through its whole life and passes it to its offspring. Due to the presence of these foreign proteins the fish brightly glows in UV light.

Transgenic form prefers warmer water — about 26 °C. There wasn’t observed any differences in keeping, feeding and breeding of genetically modified fish: the transgenic fish is the same peaceful and undemanding in terms of care.

Common NameGloFish Danio
Scientific NameDanio rerio
AppearanceSmall, slender fish with elongated body
Size1 to 2.5 inches (2.5 to 6.3 cm)
ColorationVibrant fluorescent colors (red, orange, green, yellow, blue, purple, pink)
Lifespan2 to 4 years
Temperature Range72°F to 78°F (22°C to 26°C)
pH Range6.5 to 7.5
Water Hardness5 to 15 dGH
CompatibilityPeaceful, can be kept with other small fish
Tank Size10-gallon minimum for a small group
DietOmnivorous, will accept flake and live/frozen foods
BehaviorActive, schooling fish
Breeding MethodEgg scatterer, non-guarding parents
Special ConsiderationsRequires adequate filtration and regular water changes
Genetic ModificationGenetically modified with fluorescent proteins from other species
Legal StatusApproved for sale in some countries, check local regulations

GloFish sharks

As you know now – the above mentioned fishes are modified version of fishes that inhabit in the wild. Before buying modified fishes I recommend you to read our articles about Red-tailed black shark and rainbow shark. These fishes are graceful, good-looking, active, but not as harmless as they may seem, therefore it is strange, that the company chose them to perform its experiments.

The thing is that, first of all such modified fishes are bought by beginners attracted with their appearance and they may become quite disappointed later, when they find out that genetically modified fishes are not that easy to keep.

Scientific NameEpalzeorhynchos frenatus
Common NamesGloFish shark
Range and habitatIndochina
Size6 in (15 cm)
Lifespan4-6 years
Ease of keepingDifficult
Minimum tank size30 gallons (136 litres)
Temperature21–27 °C (70–81 °F)
Water hardness5-20 dGH