Fact Check: The Internet Says a Goldfish Kept in a Dark Room Will Eventually Turn White. True?

Madison Dapcevich
·6 min read
18
goldfish.
Getty Images/Stock Photo

Claim:

A goldfish kept in a dark room will eventually turn white.

Rating:

Rating: Unproven
Rating: Unproven

If you keep a goldfish in a dark room long enough, will its skin eventually turn white?

It’s a question that has spread across the internet for more than a decade. Through a simple Google search, Snopes found anecdotal references to the claim on nearly every social media platform – and even a digital Snapple bottle lid – including posts shared to YouTube, Facebook, Reddit, Pinterest, Instagram, Quora, and X:

The theory behind it is that if a goldfish is deprived of sunlight, its skin will lose pigmentation and turn white. Despite its prevalence, this rumor appears to be nothing more than an old fisherman’s tale. Snopes was unable to find scientific evidence to corroborate the claim and, as such, we have rated it as Unproven.

At Snopes’ request for an interview, the Florida Museum of Natural History put us in contact with Rob Robins, collection manager of the Division of Ichthyology, who said there is no evidence a goldfish will lose its namesake hue when shut in a dark room.

To understand why this rumor is unproven, we must first dive into the physiology of fish.

Fish have two layers of skin: the outer epidermis and the inner dermis, or corium. The color of these skin layers is impacted by a combination of genetics, biological pigments, structural color, and diet – not sunlight. The University of Florida writes:

The skin color in fishes is principally genetically determined, and skin color can be inherited from generation to generation. Genes regulate a variety of processes that determine how much of a specific pigment type, like melanin, is produced, and how it is deposited in the chromatophores. Pigment types range from dark to light black, gray, brown, orange, yellow, and red. However, not just one but several genes influence skin color, permitting the environment to have greater control over variation in skin color, and making the process of selective breeding for fish skin color more problematic and slower.

Fish primarily obtain their color by eating food that contains biological pigments (biochromes) which are then absorbed, metabolized, and deposited into specialized skin cells known as chromatophores. Different types of pigments may influence a fish’s coloration. For example, melanin is responsible for darker colors like browns and yellows, as well as dark gray and black tones. Meanwhile, chlorophyll found in algae can create green hues while carotenoids found in fruits and vegetables produce blue, yellow, orange, green, and red pigmentation.

In response to hormonal changes and nervous system or environmental stressors, some fish can control the pigment-producing chromatophores to change their colors. When spawning, salmon change color to attract a mate while the pointy-snouted reef fish can change from white to reddish brown in response to environmental changes.

In addition to chromatophores, iridophore cells can also give coloration, according to the Australian Museum. Whereas chromatophores are found in the dermis layer of the skin and contain true colors, iridophores contain reflective guanine crystals that act as mirrors to reflect light. These reflective or iridescent colors are considered structural coloration, meaning they transmit light to produce various colorations.

While a number of factors may influence the color of a goldfish, a lack of sunlight has not been proven to turn the ornamental pets white.

“If such a procedure did have such a result, and the animal did not die from the treatment, probably people would be capitalizing on the unpigmented version [and] selling them,” Robins told Snopes in an email.

Sources:

Adkins, JoAnn. “Scientists Reveal How Color-Changing Fish Know When They Are the Perfect Shade.” FIU News, https://news.fiu.edu/2023/scientists-reveal-how-color-changing-fish-know-when-they-are-the-perfect-shade. Accessed 20 Nov. 2023.

Amiin. “TIL That If You Keep a Goldfish in the Dark Room, It Will Eventually Turn White.” R/Todayilearned, 15 Sept. 2012, www.reddit.com/r/todayilearned/comments/zwl92/til_that_if_you_keep_a_goldfish_in_the_dark_room/.

Did You Know That a Goldfish Will Eventually Turn White If Kept in a Dark Room? #shorts #facts. www.youtube.com, https://www.youtube.com/watch?v=KIJO4Yi2Mpg. Accessed 20 Nov. 2023.

FA192/FA192: How Ornamental Fishes Get Their Color. https://edis.ifas.ufl.edu/publication/FA192. Accessed 20 Nov. 2023.

Facebook. https://www.facebook.com/WoreeSS/posts/did-you-know-if-you-keep-a-goldfish-in-a-dark-room-it-will-eventually-turn-white/4900004840105179/. Accessed 20 Nov. 2023.

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“How Long Does It Take a Goldfish to Turn White If Left in the Dark?” Quora, https://www.quora.com/How-long-does-it-take-a-goldfish-to-turn-white-if-left-in-the-dark. Accessed 20 Nov. 2023.

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“If You Keep a Goldfish in a Dark Room It Will Eventually Turn White..... Yes a Goldfish Produces Melanin. Melanin Is a Pigment… | Goldfish Tank, Fish Tank, Goldfish.” Pinterest, https://in.pinterest.com/pin/222083825348027920/#:~:text=Coldwater%20Fish-,Common%20Goldfish,Without%20light%20the%20pigment%20fades. Accessed 20 Nov. 2023.

Instagram. https://www.instagram.com/p/Cyv3y1xy-TY/?img_index=1. Accessed 20 Nov. 2023.

News, Opening Hours 10am-5pm Mon-SunExtended hours for Ramses ticket holdersClosed Christmas Day Address 1. William StreetSydney NSW 2010 Australia Phone +61 2. 9320 6000 www australian museum Copyright ©. 2023 The Australian Museum ABN 85 407 224 698 View Museum. “Fish FAQ - Can Fishes Change Colour?” The Australian Museum, https://australian.museum/learn/animals/fishes/can-fishes-change-colour/australian.museum/learn/animals/fishes/can-fishes-change-colour/. Accessed 20 Nov. 2023.

Robert H. Robins. https://www.floridamuseum.ufl.edu/museum-voices/rob-robins/. Accessed 20 Nov. 2023.

“Snapple Fact #34.” Snapple Fact, http://snapplefact.com/?q=34. Accessed 20 Nov. 2023.

Why Do Salmon Change Color and Die after They Spawn? | U.S. Geological Survey. https://www.usgs.gov/faqs/why-do-salmon-change-color-and-die-after-they-spawn#:~:text=Salmon%20change%20color%20to%20attract,to%20the%20ocean%20after%20spawning. Accessed 20 Nov. 2023.