How Are GloFish Made?

Written by Ricky

If you have been shopping for fish lately, you might have caught a glimpse of a new brand of fish being marketed called GloFish. These neon colored beauties have fluorescent scales that glow under a blue light. The GloFish company that makes these fish also sell a line of aquarium kits and food to keep these fish glowing bright and are particularly enticing to children. If you are considering a purchase of anything from the GloFish brand, you might have some questions about these magical looking fish. What are GloFish, and how are they made?

GloFish are made by genetic modification. This means that the GloFish company, which patented these fish, edited the DNA of a few species of common aquarium fish to produce a naturally-occurring fluorescent glow. The GloFish that you find at your local retailer are born that way- those glowing genes that were originally edited by the GloFish company are passed down from parent fish to offspring. The assortment of candy colors that these fish come in might seem like something out of a science-fiction movie but rest assured that these fluorescent colors are all naturally occurring in nature. The original genes of these fish are often combined with the glowing features of jellyfish and coral to achieve those out-of-this-world color combinations.

All of the GloFish available are either tetras, danios, tiger barbs or sharks. They are just as hardy as their non-glowing counterparts, and make excellent choices for beginner aquarists. They are also make great classroom fish, and can lead to some interesting discussions on genetics and DNA.

A Brief History of GloFish

The company behind the GloFish phenomenon did not start out with pet fish in mind. Scientists have been studying fluorescence in nature for many years. Fluorescence is the scientific term for when an organism in nature gives off a glowing color under blue light. Aside from GloFish, this nifty evolutionary trait can be found in phytoplankton, corals, jellyfish, and 180 other known species. It is believed that organisms use fluorescence for a variety of reasons, from communicating to each other to reacting to the environment. Scientists have been studying these unique hereditary traits for decades, and these creatures are used to study molecular biology and gene therapy.

The first ‘GloFish’ was a zebra danio that was part of a larger experiment meant to help identify polluted water. In 1999, scientists at the National University of Singapore introduced GFP (green fluorescent protein) that they extracted from the DNA of a jellyfish into the embryo of a zebra danio. This GFP contained the genetic information  that jellyfish use to create a green glowing light. The result of this experiment was a zebra danio that glowed fluorescent green, both under ultraviolet and natural light.

The goal of this experiment was to engineer fish who turn fluorescent in the presence of polluted water- which would be extremely helpful in identifying bodies of water that are in danger of becoming too polluted for human use. Creating the glowing green zebra Danio was the first step of that larger goal. Shortly after this Danio was created, they were able to extract other fluorescent color genes from other naturally glowing organisms, such as sea coral. It wasn’t long before the patent for this modified fish came under the ownership of Yorktown Technologies, who branded this unique new strain of aquarium fish GloFish. Although these fish are now best known as the attractive new aquarium pet, the company is still very supportive of the anti-pollution initiative for which the original GloFish was bred. They donate a portion of their proceeds directly to the lab in which they were created to further their anti-pollution research.

Are GloFish Ethical?

At first glance, you can totally tell that GloFish were part of a science experiment. The shockingly bright colors seem totally unnatural, and the thought of genetically modifying a fish might sound unpleasant at first. However, GloFish are not dyed, injected, or harmed in any way to achieve their bright colors. Each GloFish inherits the fluorescent trait from it’s parents, and they are born bright and beautiful. Selective breeding has been used for centuries in fishkeeping (and with all pets in general), and many of the species that we commonly see today as pet fish started out as genetic mutations. For example, all varieties of fancy goldfish started out as mutations that were selectively bred to keep that trait- which is why you see so many strange configurations like bubble-eyes, ryukins, and black moores. All goldfish varieties were domesticated from the wild carp of east Asia, which look nothing like the modified pets we keep today. That being said, if genetically modified fish are something you don’t feel comfortable with, you might want to consider other colorful fish varieties on the market- just make sure you don’t take home a ‘painted’ fish, or other altered variety.

There are some fish that are sold in pet stores that are not genetically vibrant, but that are altered that way in order to sell. “Painted” fish can refer to many different kinds of fish that are often injected with colored dye to create a vibrant splash of color. This process has a high mortality rate, and the fish who do survive are often short-lived and prone to infectious diseases. In addition to injecting, there are also methods that involve dipping the fish in irritating dye, or feeding the fish large quantities of dyed food to change their color. Any one of these methods is damaging to the fish, and considered an unethical purchase- not to mention all of these dying methods are not even permanent, meaning that eventually the color will fade until you have a very pale and plain looking fish. Avoid any fish that have “painted” in the name, and always do a little bit of quick research before making a purchase that seems like it could be a dyed fish.

Are GloFish hard to keep?

The GloFish brand refers to several species of fish that are available with the patented fluorescent gene. GloFish currently offers glowing versions of Zebra Danios, Tetras and Long Fin Tetras, Tiger Barbs and Rainbow Sharks. Each of these species comes in several colors that are unique to the GloFish brand: Starfire Red®, Cosmic Blue®, Electric Green®, Galactic Purple®, Sunburst Orange®, and Moonrise Pink®.

These fish species are commonly used in labs because they are extremely hardy and easy to care for. GloFish are just about as hardy as their non-glowing counterparts- perhaps a bit less so due to the editing of their genes, but no less hardy than an albino fish would be compared to the rest of it’s species. Danios, Tetras, Barbs and Sharks are great beginner fish and are great fish for children due to their active natures and colorful scales. These fish are meant to be housed in a community tank, so a large tank is recommended in order to accommodate a larger number of fish. The GloFish sharks, which are modified from Rainbow Sharks, are an exception- it is suggested that you only have one of them in a tank due to their territorial tendencies. A 10 gallon tank is recommended, and would provide plenty of room for every color of the GloFish rainbow. The GloFish brand sells several aquarium kits, complete with the blue light required to get your GloFish to really shine, at a variety of sizes and price points. They also sell gravel substrate, faux plants and other aquarium decor that responds to the glow of the blue light- so you can create an otherworldly aquarium with some space-age glowing effects.

Are GloFish bad for the environment?

Since there are no dyes or chemicals involved in the creation of a GloFish, there is no reason to believe that these fish would be harmful to the environment. As with all domestic aquarium fish, you should never release them into the wild. However, since these are all species of tropical fish, none of them are able to survive long in North American waters, so there is little danger of them becoming an invasive species should they get loose in a natural setting. Despite their strong coloring, they are not radioactive! Any potential predator that would potentially eat a GloFish in the wild would not become sick in any way- nor would it start to glow. The fact of the matter is that although GloFish originated from some genetically modified stock, they are the same as any other pet fish and will not impact the environment.

In fact, you could argue that since GloFish were developed in a lab to help combat water pollution, purchasing a set of GloFish will actually have a positive effect on the environment. The original lab is still up and running today, and working to better identify water bodies that are in danger of becoming polluted. The GloFish company donates a portion of all their proceeds back to this original lab so they can continue this eco-friendly research.


GloFish are a responsibly created and hardy fish that are great for beginners and kids. There is nothing about the way that they are made that should cause any concern for the ethical fish keeper, and the company that sells them does a great job in their efforts to give back to the research community. All in all, GloFish are a great choice for a home aquarium, and the unique glowing colors are sure to be a conversation starter.

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