glofish in an aquarium
Glofish image from

Glofish is the name given to genetically modified zebra danios (Brachydanio rerio). Their name is correctly spelled as glofish, but is sometimes incorrectly spelled as glowfish. This is a common mistake because the fish do seem to glow when they encounter environmental toxins.

When I first wrote this article, zebra danios were about the only glofish available, and these are the kind pictured above, but now there are many more glofish breeds available. Currently, glofish are available in the following species:

  • Barbs
  • Bettas
  • Danios
  • Sharks
  • Tetras

The difference between regular zebra danios and glofish are that researchers in Singapore added a fluorescence gene from a sea coral to zebra danio eggs to produce glofish. This gene causes the genetically modified fish to fluoresce or light up in the presence of environmental toxins.

Other than this, they are identical to regular zebra danios, with the exception that the genetically modified glofish have neon colors. Regular zebra danios are gold and blue striped or gold and silver striped fish. Both glofish and regular zebra danios are peaceful fish that do well in a community tank.

Originally created to detect environmental toxins, glofish have been for sale in pet stores since 2003 for the general public to buy and place in their aquariums. There is some concern about what might happen if these genetically altered fish find their way into natural rivers and streams. The creators of glofish state that they don't pose an ecological threat because glowfish, like regular zebra danios, won't survive in the wild because they are tropical fish and need a water temperature of about 24-26 °C (75-79 °F). It's been 17 years now and so far there doesn't seem to be a problem. Although some people do question the ethics of selling genetically altered fish to the public just because they are prettier than the original fish.

Glofish come in a variety of colors, including red, green, and orange. They can be purchased for about $6-7 each.

Glofish are reported to be as healthy as regular zebra danios and their care is identical. They reach an adult size of approximately 2 inches (5 cm). They are omnivores that eat a variety of aquarium fare.

I have had some tetra glowfish in my aquarium for some time now and they seem to be happy, healthy fish so the fact that they are genetically modified doesn't seem to hurt them.

Glofish Breeding

Glofish will breed and spawn in exactly the same way as whatever species of fish they are. However, it has come to my attention that it is not permissible to purposefully breed them. This is because glofish are patented and you cannot breed and sell them or trade them with other aquarists. However, if some should unintentionally spawn in your tank...

For more information please see On their site you'll find more information about glofish, pictures of other glofish species, and the option to order glofish online.