There is a lot of confusion surrounding the “breed” of curled-gill goldfish. They seem to be very rare and unusual, yet there is not much specific information about them. Even though they have been around since the beginning of the trend involving breeding ornamental goldfish, they are not very prolific.

We answer all your questions and more about curled-gill goldfish in this article.divider1- goldfish

Curled-Gill Goldfish: The “Breed”

The curled-gill goldfish is not a breed of goldfish at all. Instead, the curled gill is a genetic disorder or health issue that develops as a fish ages.

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Fish that appear to have curled gills will look the same as other goldfish of the same species. The difference will be that instead of fanning outward, your fish’s gills will be dark and will curl toward their bodies in a pronounced bump. The gills will often become a dark purple or deep red.

Some goldfish breeders and enthusiasts have tried breeding fish with a curled gill to produce a species with this specific trait. However, it has thus far been proven to be a non-transferable characteristic between parents and fry.

Not only is the curled-gill goldfish not a separate breed, but the curled-gill characteristic can appear in almost any kind of ornamental goldfish.goldfish divider

Curled-Gill Goldfish: The Disorder

In reality, although the curled gills on these goldfish is an interesting physical trait, it does not bode well for your fish.

The condition has appeared in many different types of goldfish from the beginning of ornamental goldfish development. Yet there is still quite a bit of confusion regarding the origins.

There are two primary reasons for a goldfish to have curled gills: they may have been born with a natural deformity caused by a rare genetic disorder, or they suffer from ammonia poisoning.

Genetic Disorder


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Although the general public has become accustomed to goldfish species that look pristine, physical deformities are quite common. Hatchlings often have issues with the proper formation of their gills, fins, or lips, most of which do not impact their quality of life.

However, in this industry, like many others, breeders believe that these abnormal fish won’t sell and quickly cull them from their schools to cut their losses. Often, they justify this since many sellers won’t buy these deformed fish.

Fish with curled gills are frequently among those that are culled from schools of fish. That is the primary reason we do not see them in pet stores very often. However, some collectors around the globe will pay higher prices for these unusual fish.

Ammonia Poisoning

dead goldfish

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Ammonia poisoning is the more frequent causal agent for curled-gill goldfish. Ammonia is extremely toxic to fish. The recommendation is to keep the ammonia level in the tank as close to 0 parts per million (ppm) as possible.

If fish begin to experience ammonia poisoning, they suffer from extreme discomfort and even pain. You will notice that they hold their dorsal fins tightly to their sides, even after the ammonia levels lower within their environment.

The most significant factor in how ammonia hurts fish is that it prevents them from taking in the oxygen in the water. Goldfish typically breathe the water into their mouths and then push it out through their gills, absorbing oxygen along the way.

However, ammonia exposes the organs to toxins and causes internal cells in their gills to swell up. It leads to oxygen loss and will ultimately lead to death in severe cases.

If you catch raised ammonia levels early enough, you can reverse the process and save your fish. Even if the fish lives, their gills are likely to have been permanently changed in cases that were damaging. Curled gills are often the result of being poisoned from ammonia multiple times.

Repairing Damaged Gills

As a birth defect, curled gills do not typically damage or shorten a fish’s life. If curled gills result from ammonia poisoning, then they should be carefully monitored. Keep your curled-gill goldfish safe, carefully measuring ammonia levels and keeping the tank clean.

Some experts recommend using massage therapy on fish whose gills have ended up curling from poisoning. However, this area of their body is the most sensitive, and you can end up doing much more damage than good.

Unless you know precisely what you are doing, it is best to leave the fish alone in a healthy environment. The curled gills are a reaction to ammonia poisoning but are not signs that the fish is still in any pain or discomfort after the levels lower.divider4-bubbles

In Summary

Curled-gill goldfish is not an actual breed of goldfish. The genetic deformity is nontransferable and can occur among any species of ornamental goldfish. It also commonly occurs in fish that have lived through ammonia poisoning. Curled gills do not normally affect the fish’s life and should be left alone so they can live out a happy existence.

Featured image credit: Michelle Jo, Commons Wikimedia