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Is it Cruel to Keep Glofish?

Updated on November 11, 2016

Many people are seeing glofish in pet stores, and naturally wonder whether these fish are hurt when they are made these bright colors or experience poor welfare. This Hub will answer the following questions:

  • How are glofish created?
  • Does this process cause suffering to the fish?
  • Is their welfare affected in any other ways?
  • Are glofish dangerous to the environment?

How Are Glofish Created?

Glofish are small aquarium fish species that have been genetically modified to have bright luminescent color. They were first developed to create a more easily visible fish for use in water quality research.

The first glofish, zebrafish (Danio rerio) were made generally available for sale in 2003. Since then glofish vatietries have been developed for Black tetra (Gymnocorymbus ternetzi)and tiger barb (Puntigrus tetrazona).

Glofish are now available in six colors: red, orange, pink, purple, blue and green. However the blue variety does not have the vivid glow of the other types.

Glofish Danio rerio -- djwtwo / photo on flickr

Does this Process Cause Suffering to the Fish?

There are processes that hurt and damage fish such as injecting dye into their bodies. However possession of the glo gene is passed from parent to offspring fish, and causes no discomfort to the fish. Thus there is no need to avoid these fish for reasons of animal welfare.

In contrast fish that are physically injected with dye ("painted" fish) often experience health problems and discomfort as a result--these fish should never be bought.

Is their Welfare affected in any Other Ways?

This is a subject that I do not have an objective data on. However, I have observed that when glofish and wild type danio (zebrafish) are kept in the same tank, the glofish age quicker and die younger. By 'age quicker' I mean the show reduced vigor, a loss of muscle mass, and bending of the spine at a younger age than the non-modified fish. This may reflect the increase metabolic burden of being brightly colored and luminescent--leading to the animals being under a greater strain and thus more prone to deteriorating health as they age.

Black tetra (Gymnocorymbus ternetzi)--glofish vatiety
Black tetra (Gymnocorymbus ternetzi)--glofish vatiety

Are Glofish Dangerous to the Environment?

Some commentators worry that glofish are not well-regulated. They are concern that these fish might be released into the wild (Knight, 2003).

The risk associated with glofish should be limited as they are intended to be infertile. However multiple aquariists have reported that their glofish were able to reproduce. If not between each other than between normal zebra fish and the glofish variety.


In conclusion the keeping of glofish is not cruel in that the genes are not a direct cause of suffering for the fish. However, fish without these genes may have an overall better quality of life. Thus buying these fish is not obviously unacceptable on welfare or environmental grounds, some people may still choose to avoid buying them as the welfare of non-modified fish is likely to be better.


Do you think it is ethical to keep glofish?

See results


  • Knight, J. (2003). GloFish casts light on murky policing of transgenic animals. Nature, 426(6965), 372-372.


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    • wpcooper profile image

      Finn Liam Cooper 

      15 months ago from Los Angeles

      Well i used to have fish when I was younger and tried it recently and ended up killing them. I had no idea that goldfish were created. nice article.

    • psycheskinner profile imageAUTHOR


      2 years ago

      The GM modifications in animals are still very rare in the public sphere. I struggle to think of any animal available to purchase other than the breeds of glofish. As for ho they look, that is a matter of aesthetic taste. I find many toy breeds of dogs far more offensive because their deformities cause the animal suffering. I think that is more important than how the change in the animal was produced.

    • jupiter justice profile image

      Asher Socrates 

      2 years ago from Los Angeles, CA

      Unfortunately modifications are wide spread and not only in fish. Everything has been subjected to this in many ways. I've seen these fish before and they look ridiculous. We should ask ourselves, why do we all allow profit to change the balance of the way life and nature were intended?

    • Blackspaniel1 profile image


      3 years ago

      I have never heard of this before. Thanks.


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