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Home > Goldfish > The Truth About Curled-Gill Goldfish: Vet-Reviewed Science & Info!

The Truth About Curled-Gill Goldfish: Vet-Reviewed Science & Info!

Curled gill goldfish

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It may be startling to come across a goldfish with curling gills, as it looks unnatural and stands out on a goldfish. Your first thought might be that these goldfish are ill, but this is far from the truth. Curled-gill goldfish (also known as reversed gill goldfish) are the result of a genetic deformity or mutation.

There is a lot of misinformation on how curled-gill goldfish came to be and what is the exact cause for this genetic problem to occur, but in this article, we hope to clear this up!


What Does a Curled-Gill Goldfish Look Like?

Goldfish with curly gills will have a curved outer gill covering (operculum) which exposes the deep red or purple membranes that the gill plates cover on a normal goldfish. Curled-gill goldfish look like an average goldfish, except their gills are curled and the membranes below are exposed. Fancy goldfish are more likely to be affected by this genetic deformity, with it being most common in Ranchu, Fantails, Ryukin, and Pearlscale goldfish.

In some instances, the goldfish might also have a kinked fin, but this is rare. The sight of a curled-gill goldfish may seem abnormal at first, but the only difference between a normal goldfish and a fancy goldfish is the way that the operculum is positioned. It is also possible for a goldfish to have one curled gill and the other one normal, as it all depends on the goldfish’s genes.

Image Credit: Michelle Jo, Wikipedia Commons

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What Causes a Goldfish’s Gills To Curl?

A genetic mutation is the main reason for a goldfish to have curling gills. Gill-curling in goldfish does not seem to be a hereditary condition that is transferred from the parents to the fry. Most goldfish breeders will cull the fry showing signs of a deformity such as a curling gill or fin, which is why these types of goldfish are not that common and are sometimes sold for a cheaper price at a pet store than other goldfish.

Aside from a true curled-gill goldfish being born with this condition, certain situations can cause your goldfish to look as if they have curling gills.

  • Ammonia poisoning: High levels of ammonia present in your goldfish’s aquarium or pond can cause their gills to swell, which can give their gills the appearance of being curled. However, the gills are not truly curling. The gills may turn red and swell as your goldfish is being burned from the harsh ammonia, but it does not cause a lasting curling effect on your goldfish. Goldfish can tolerate low levels of ammonia below 0.25 ppm (parts per million), but the ideal level of ammonia in a goldfish aquarium should be 0 ppm.
  • Nitrate poisoning: High levels of nitrates in an aquarium can cause your goldfish to have a bent appearance and form a “C” shape when viewed from the top. This can cause one of the gills to stick up. Goldfish are more tolerant of nitrate in comparison to ammonia and nitrites and can handle low levels (typically below 20 ppm) of nitrates until they start to show symptoms of being poisoned. Nitrate poisoning is usually caused by extremely poor water conditions.
  • Disease:Certain diseases can cause your goldfish’s gills to become inflamed and bizarre in appearance. This will make the gills work overtime, as severe diseases can cause major discomfort to your goldfish. The gills may swell, and in some cases, parts of the gill will rot away if the disease is not treated promptly. Many gill ailments are fatal if left untreated.
  • Injury: Physical damage can cause an injury or tear to a goldfish’s gill, which can make it appear as if it is sticking out or curling. This can happen if your goldfish has scraped their gill on a rough object, gotten a piece of substrate lodged in their gill, or if they have tried to squeeze through a tight-fitting place and dislodged their operculum.

It is important to note that these situations can cause your goldfish to only appear as if they have a curled gill, and it does not make them curly-gilled goldfish.


Can Curled-Gill Goldfish Live a Normal Life?

Most curled-gill goldfish can live a normal life and live a lengthy lifespan, as this deformity rarely seems to affect how their body functions. They are, however, more vulnerable than other goldfish because they do not have their operculum fully protecting the delicate red or purple membrane that lies below.

The average lifespan of a curly gilled goldfish is usually the same, but there is little documentation on how long these goldfish can live because they are so uncommon. Environmental factors or diseases are usually the main cause of death with curled-gill goldfish, which makes it difficult for goldfish enthusiasts to keep track of exactly how long these goldfish can live.

There is no cure for a goldfish with curling gills, and if they are healthy and showing no signs of being in distress from their condition, then you should not have to worry about how their gill deformity is affecting their quality of life.

panda oranda goldfish
Image By: Wisnu Bangun Saputro, Shutterstock


Final Thoughts

Curled-gill goldfish are born with this condition and can live a relatively normal life if they are kept in a suitable environment and fed a healthy and balanced diet. Although their appearance is affected, curled-gill goldfish function the same as any other goldfish. Some goldfish enthusiasts even seek out goldfish with curly gills because they find this condition intriguing and unique.

We hope that this article has helped you better understand the phenomenon behind goldfish with curling gills!

Featured Image Credit: Curled gill goldfish (Michelle Jo, Creative Commons CC0, Wikimedia Commons)

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