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Sunday, February 14, 2016

Glofish–The first commercially viable ornamental genetically engineered fish

September 22, 2010 by  
Filed under Other Genetically Altered Fish

Initially offered for sale on December 11, 2003, GloFish® is a patented and trademarked, genetically engineered Zebra Danio. GloFish® was the first genetically engineered fish available to the aquatic hobbyists market.1 These Frankenfish are sold under the trademark names Starfire Red® (“Red Danios”), Electric Green® (Green Danios), and Sunburst Orange®. (Orange Danios) for around $6 – $7 per each.2 Yorktown Industries owns worldwide rights to all GloFish®.

GloFish® History and Genetic Engineering

Glofish picture

Photo courtesy of

GloFish® fluorescent fish were engineered at the National University of Singapore by Dr. Zhiyuan Gong and his team of geneticists.3 Originally, the plan was to use this Frankenfish to detect environmental toxins in waterways. Originally, geneticists added the fluorescent gene from jellyfish to Zebra Danio eggs, allowing it to integrate into the Zebra Danio’s genome. This caused the fish to be brightly fluorescent under both natural white light and ultraviolet light. Shortly thereafter, red fluorescent zebra fish were created by adding a gene from a sea coral, and yellow fluorescent zebra fish were created by adding a gene from jellyfish.4

The fluorescence is caused by a single gene modification made to Zebra Danio eggs before they hatch. Glofish® are born with and maintain their unique color for their entire lives. Glofish® pass this gene modification to their offspring, perpetuating this Frankenfish species.5

Excluding the single gene modification, GloFish® are identical to Zebra Danios. This includes general care, temperature preference, growth rate and life expectancy.

Do fluorescent fish glow?

Fluorescent fish absorb light and then re-emit it. This creates the perception that they are glowing, particularly when shining an ultraviolet light on the fish in a dark room.6

Does the fluorescence harm the fish?

No. Glofish® are as healthy as Zebra Danios in all ways.7

What if a fluorescent zebra fish is eaten?

Eating a Glofish® is the same as eating a Zebra Danio. The Glofish® fluorescence is derived from a naturally occurring gene. Just as eating a blue fish does not turn a predator blue, eating a fluorescent fish does not turn a predator fluorescent. Even though the Glofish® is a Frankenfish, eating one does not result in Frankenfish symptoms.8

GloFish® Gender
Unlike Zebra Danios, male and female GloFish® are virtually the same color. The only way to differentiate between male and female is by body shape. Adult males have a streamlined shape. As they mature, adult females develop a “paunch” that is identical to that of a female Zebra Danio. Female stripes have a brighter gold tone as well.

Environmental Concerns
Environmentalists are concerned that these Frankenfish could cause irreversible ecological damage to rivers and streams if released. However, Yorktown Industries emphatically asserts that Glofish® are not a threat. GloFish®, like natural Zebra Danios, can survive in tropical waters only (temperature between 64-74° F).

On December 9, 2003, FDA issued the following statement:
“Because tropical aquarium fish are not used for food purposes, they pose no threat to the food supply. There is no evidence that these genetically engineered Zebra Danio fish pose any more threat to the environment than their unmodified counterparts which have long been widely sold in the United States. In the absence of a clear risk to the public health, the FDA finds no reason to regulate these particular fish.”9
Since 2003, when they were first made available to aquarium enthusiasts, no ecological damage is apparent.

Glofish image

Photo courtesy of

GloFish® Breeding
Glofish® are patented, and therefore intentional breeding is illegal without proper licensing provided by Yorktown Industries.10

However, if GloFish® spawns naturally in the hobbyist aquarium and the fry are not offered for sale, the aquarium enthusiast does not have to apply for any special license.
Glofish® offspring will be GloFish® and not Zebra Danios.

About Zebra Danios (Brachydanio reri)

Zebra Danios belong to the Cyprinidae family. Native to rivers in eastern India and Bangladesh, Zebra Danios are a hardy and active fish with peaceful temperaments. Provided they are placed in tanks with fish of similar temperament, they make good additions to aquariums. In the United States ornamental fish market alone, more than 200 million Zebra Danios were sold over the last 50 years.11

Zebra Danios will live for about five years and will grow to length of about two inches (about 3 centimeters). They thrive in slightly acidic to neutral water (pH 6.5-7.0) and water temperatures of 64-74 degrees Fahrenheit. They can, however, adapt to the warmer water temperatures needed by other tropical fish. Zebra Danios are surface dwelling fish that prefer moving water. Zebra Danios are shoaling fish. Nature intended Zebra Danios to live in schools, so it is best to purchase several for an aquarium.

Zebras Danios are omnivores. A diet of tropical fish flakes will keep them healthy.

Zebra Danio Gender
Females have blue and silver stripes and have a more rounded body shape. Males have blue and gold stripes. Both genders have two pairs of barbels on either side of their mouth. Females tend to be larger than males.

Zebra Danio Breeding
Zebra Danios are some of the easiest fish to breed. For best success, it is important to have two tanks, one for adults and one for spawning. Adult Zebra Danios eat their own eggs, so once spawning is complete, the adults should be moved to the adult tank. For best results, place marbles in the bottom of the spawning tank and add plants to provide the fry some cover.

During spawning, females scatter about 300 – 500 eggs across the tank floor. Eggs typically hatch in 1-3 days. Once the fry are free-swimming they can be fed liquid fry food or infusoria. After about 10 to 14 days, add brine shrimp nauplii, powdered fry food and or tropical fish flakes to their diets.

Spawning can be triggered by raising the water temperature up a few degrees near dawn. This will trick the fish into believing it is mating season.

What are the differences between GloFish® and Zebra Danios?

Aside from their brilliant color, GloFish® are the same as Zebra Danios in every way. This includes general care, temperature preferences, growth rate and life expectancy.

GloFish® are illegal to import or sell in many countries including, but not limited to the European Union, Australia, Japan, and Canada. In these countries, if caught, shop keepers face fines, prison terms and loss of business operations.
GloFish® in California

Glofish® received a positive recommendation from the California Department of Fish and Game in November 2003, and the California Fish & Game Commission voted to move forward with the process of exempting Glofish® from their ban on biotech aquatic organisms in April 2004. However, Yorktown Industries, subsequently advised by Commission attorneys that state law in California would require the completion of a formal ecological review to comply with the California Environmental Quality Act before the Commission could move forward with the approval process. This review is extremely expensive, involves procedural uncertainty, and takes several years to complete.
Due to the excessive cost and time involved in that process, as well as the uncertainty, Yorktown Industries decided skip the review.12

glifish licensinc picture

Yorktown Technologies posted a License Notice at This notice outlines the restrictions on breeding or selling the fish. It also includes information on the intellectual property rights covering these fish.

GloFish® Ethics – (From GloFish®.com)
The following is Yorktown Industries Code of Ethics. This code of ethics may be found on

Glofish green image

Photo courtesy of

glofish ethical principles


Fluorescent Fish Data & Research
Discovery Genomics Research Regarding Fluorescent Zebra Fish Temperature Sensitivity (pdf)

Abstract: National University of Singapore Fluorescent Zebra Fish Viability Study

Abstract: Behavioral Study Comparing Non-Fluorescent and Fluorescent Zebra Fish

Federal & State Agency Reviews
United States Food & Drug Administration Statement Regarding GloFish® Fluorescent Fish

State of Florida Division of Aquaculture Analysis of Fluorescent Zebra Fish (pdf)

State of California Department of Fish & Game Analysis of Fluorescent Zebra Fish (pdf)

Reviews by Independent Experts

Environmental Risk Analysis by Dr. Zhiyuan Gong (pdf)

Environmental Risk Analysis by Dr. Perry Hackett (pdf)

Environmental Risk Analysis by Dr. Eric Hallerman (pdf)

Environmental Risk Analysis by Dr. William Muir (pdf)

Fluorescent Protein Toxicity Analysis by Dr. Andrew Cubitt (pdf)

General Zebra Fish Background Data
United States Geological Survey Zebra Fish Fact Sheet

FishBase Zebra Fish Species Information

History of Zebra Danio Distribution within the United States (pdf)

Additional Information

“Zebra Fish as Pollution Indicators,” National University of Singapore

Fluorescent Fish in Biomedical Research

Article: “Zebrafish Genetics,” Mayo Clinic’s Discovery’s Edge

Website: Fish For Science – Zebra Fish as a Model Organism

Fluorescent Zebra Fish in Emory University Cancer Research Study

Article: “Following the Glow: NC State Researchers Use Fluorescent Fish to Study Gene Function,” North Carolina State University
End Notes

1..(2003) Press Release: Yorktown Technologies Announces Early Availability of GloFish® Flourescent Fish


3.(2003) Press Release: Yorktown Technologies Announces Early Availability of GloFish® Flourescent Fish

4. (2010) Wikipedia

5. (2010) Fishmart®

6. (2010) Fishmart®

7. (2010) Fishmart®

8. (2010) Fishmart®

9. (2003) FDA Statement Regarding Glofish FDA Veterinarian Newsletter November/December 2003 Volume XVIII, No 6

10. (2010)

11. (2010)

12. (2010)

13. (2003 (Why GloFish won’t glow in California Sam Schuchat Wednesday, December 17, 2003)

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