WHY is your fish losing scales? Do they grow back? (2024 guide)

Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: May 6, 2024
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Allocating some time daily to examine the condition of our hopefully flourishing fish is a gratifying task. Nonetheless, despite our attentive watch, it can be quite challenging to detect the subtle changes in our water friends’ health when they are sick.

Article Summary

  • Fish losing scales can be alarming for fish owners, but understanding the causes and solutions is crucial.
  • Fish don’t naturally shed scales; their scales protect them from various threats.
  • Scales can grow back over time, but the rate varies between species.

Seeing our beautiful fish in distress can be a nightmare for any goldfish owner especially if we don’t know why – so it can be alarming when our quiet water friends begin to get sick or hurt.

Luckily for the intrepid home aquarist, we’ve gathered a guide to some of the more common problems that cause goldfish to shed their scales, along with tips on how to solve them.

Follow along to learn more about how to build a healthy life for fish suffering from scale shedding.

Why Is My Fish Losing Scales?

This is the first question any concerned home aquarist may ask when looking at a potentially injured or sick pet.

The real answer is that there are multiple reasons, many of which are in the control of the pet owner. The good news is, for a majority of these issues there are concrete solutions, which we’ll discuss today.

What Causes Fish Scale Loss?

Yellow Fish Side View
Yellow Fish Side View

Physical damage, infection, and disease are the most common methods by which many scales can be lost at once. Throughout this article, we hope to illuminate each of these individually, to provide a better understanding of how each can be identified, treated, and prevented in the first place.

What Does It Mean If Your Fish Is Losing Scales?

A fish in distress from any of the previously mentioned reasons will likely lose scales as a result. Keeping an eye out for the key signs and symptoms of these ailments is critical to assessing the health and safety of our underwater friends, and can provide insight into what exactly is wrong.

What to look for with goldfish scale loss

  • Patchy or raised scales
  • Bruising
  • Swelling and redness
  • Abnormal behavior such as swimming at the surface, loss of appetite, and lethargy

Do Fish Shed Their Scales?

Fish do not naturally shed their scales. Unlike reptiles, fish grow larger and do not molt but keep the same number of scales for their entire lives. Under normal circumstances, fish scales protect fish from predators, disease and physical damage. When fish shed it is typically a sign of distress, injury or sickness.

Can Goldfish Grow Back Their Scales?

Fish scales can grow back over time, however the rate at which these come back can vary between species depending on many factors. For some fish, scales can grow back as fast as a few days, while other species may take several months to recover shed scales (Skomal).

Physical Damage

From rough handling by careless owners, to physical altercations with tank mates, the home aquarium can be a very active place for scale loss in goldfish and others.

Goldfish owners should take care to ensure safe transport and storage of their pets. While the entire setup may be the last thing most aquarists want to think about moving, it does happen!

Not only does moving our goldfish carry the potential for physical injury, the stress caused can be equally dangerous to their health.

Use soft nets that are large enough for the fish species you’re netting to avoid damaging scales!


Fish tank decorations such as sharp objects or rough stones can lead to further missing scales. Fish that tend to swim more erratically may damage themselves against hard sides and sharp edges, and accidentally rub scales away.

Aggression Between Fish Species

Fighting or aggressive behavior in fish, especially during breeding season, is not unheard of.

Common reasons why one fish may attack another include competition for resources, territorial defending, and increased aggression during breeding season. We recommend taking a close look at breed compatibility based on a few key elements.

Here’s an informative video on what causes fish to fight.

Stopping Aggression In Your Aquarium

Size, diet, fish breed, and attitude are critical to consider when looking at potential neighbors for your goldfish. Additionally, having too many in the same tank can mean more fish die as they compete for space and resources.

Aggressive fish such as certain betta fish, cichlids and groupers are natural predators in the wild and will follow their instincts when hungry, meaning potential danger for other fish in the aquarium!


Take care when selecting a noted aggressive fish species, and note which will get along to prevent scale loss.

Stress and the Aquarium

Another way goldfish can lose their scales is from excessive stress. Poor water quality, harsh living conditions, and bad nutrition can all lead to lost scales for a goldfish.

Fish live totally immersed in their environment, meaning that the water in which they live determines how they eat, breathe and drink.

Subsequently, it is incredibly important that we monitor water parameters and note tank conditions through testing and observation.

Water that is cloudy, smelly, or generally overcrowded may be in need of attention. Fish have less access to oxygen with the presence of dangerous chemicals and may become more easily sick, or even die as a result.

Test for the presence of harmful chemicals that build up over time such as ammonia, sulphuric acid and carbon dioxide. Even in the early stage, these dangerous additions can lead to a less healthy slime coat and scales in your goldfish, meaning increased disease and fish shedding.

Water Quality

Highly polluted water in your home aquarium means less air for the goldfish to breathe, increasing strain on their hearts, disrupting their immune systems, and potentially leading to death. Infrequent water changes increase this strain even further leading to scale loss.

On the other hand, the presence of small bubbles on plants in the aquarium indicates a healthy environment full of oxygen.

When considering adding aquarium salt, remember that regular table salt contains additives and preservatives that are harmful to goldfish. To keep fish hydrated, chemicals such as iodine and cyanide must be balanced properly.


Testing kits are readily available and are a key component of regular tank maintenance and upkeep. Creating a regular schedule can be challenging at first, but with the help of family and friends in the home it can become a great group activity.

Infections Can Make Fish Lose Scales

Fish Losing Scales

Maintaining a clean, safe environment is the first step to preventing a goldfish or really any fish losing scales due to infection. Viruses, fungi, and bacteria all thrive in conditions that vary ever so slightly from the ideal, meaning close attention to detail can pay large rewards for the diligent aquarist.

Slime Coat

Many species of fish, including goldfish and the basic violet possess a protective slime coat meant to shield them from the early stages of disease and infection. Over time and with excessive damage to a fish’s scales, combined with poor water quality, this layer can break down.

The general term infection can refer to a range of illnesses or a specific disease such as infectious protrusion disease or Icthyosporidium, but most present in a similar fashion when considering fish scales.

Signs of infection include:

  • Redness, swelling, and lines of color radiating around affected scales
  • Bleeding and possible ulcers
  • Scale loss, damage, or fraying
  • Change or darkening in color of regular scales
  • Behavioral changes such as lethargy, swimming oddly, and appetite loss

Treatment for fungal and bacterial infections includes quarantining the affected fish, cleaning and replacing the water in the tank, providing proper medication and antibiotics as needed, drying out suspected decorations carrying infectious organisms, and monitoring for further health complications.

Flashing is a Sign of a Goldfish Losing Scales

When fish are feeling itchy, they use a technique called flashing to scratch themselves.

A fish exhibiting flashing is likely showing signs of an attack from a living being in the form of parasitic or fungal infections. This can include a range of invertebrate aggressors such as anchor worms, Trichodina, or Icthyobodo.

While poor water and overcrowding can increase the chance of infection, passengers traveling with new additions to the tank are the most likely cause.

Dropsy Can Make Fish Shed Scales

The term dropsy comes from an old English medical term for swelling in the abdomen caused by gases or fluids.

The “drop” refers to the way the belly of the goldfish appears to droop in appearance as it swells. Today it would more likely be referred to as an edema, but either way it can lead to serious health complications in fish.

Dropsy fish disease is caused by a group of several bacteria commonly present in most home aquariums. A healthy, unstressed goldfish can handle the presence of these bacteria without much problem.

Notable signs of a fish with dropsy

  • Swelling around the eyes and belly
  • Presence of lesions, scale loss, or abrasions
  • Becoming lethargic, or excessively tired
  • Swimming in irregular ways

Treatment for dropsy can be difficult. Moving affected fish to a separate tank can provide a place to care for them while simultaneously protecting others from infection.

The appearance of dropsy in fish is often a sign of general poor health, and as such providing a proper diet and healthy water is key.

A fish with dropsy may also show no signs or symptoms until the disease has progressed past the point of care.

Ammonia Poisoning and Fish Losing Scales

Fish Near Filter Tube
Fish Near Filter Tube

While cleaning may be a major chore for some households, a clean tank goes a long way towards preventing scale loss.

When the water in our fish tank becomes polluted by natural wastes the pH level lowers, available oxygen decreases, and harmful levels of chemicals such as nitrogen and ammonia can accumulate.

Water that comes from the tap and has been treated with chemicals may lead to excess nitrogen buildup. Additionally, the breakdown of organic materials such as plant matter, fish excrement, and uneaten food can cause a rise in ammonia levels.

Ammonia poisoning in particular can cause gill and slime coat damage in fish, leading to impaired breathing and possible death for those affected.

Signs of ammonia poisoning include:

  • Red or bluish gills
  • Swimming around the surface
  • Lethargy
  • Fish shedding scales
  • Loss of appetite

While preventing a polluted tank is the key to avoiding ammonia poisoning, these events do happen. Therefore, it’s important to know the steps to take when you suspect a poisoning in the tank.

  • As much as a 50% water change
  • Immediately change carbon filters
  • Test water in the tank
  • If water quality has not improved, try another 20% water change
  • Don’t feed the fish until conditions have returned to normal. A new cycle of feeding and excreting can bring pollution levels right back!
  • Once things improve, consider cleaning all filter media before returning to the tank

Hemorrhagic Septicemia

According to the The Center for Food Security and Public Health at Iowa State University, Viral Hemorrhagic Septicemia, or VHS is a highly infectious, fatal disease caused by a viral infection spread through the urine or reproductive material of fish. Contact from fish carrying the virus or objects in the tank can also lead to infection.

The infection can cause deadly hemorrhages, or excessive bleeding, in many different areas of the body of the fish.

Checking for Symptoms

Notable areas to check for bleeding include the base of the fins, eyes (leading to the classic “pop-eye” look), and abdomen. However, affected fish may show no signs or symptoms until bleeding has progressed beyond help and can still be contagious to others.

As with many viral infections, treatment for VHS can be incredibly challenging, however the use of antibiotics and certain medications can be effective.

Isolate the infected fish immediately to prevent further spread and continue to monitor for improvement.

Scale Shedding Disease

Also referred to as scale protrusion, bacterial infection can cause goldfish to shed their scales. The likely culprits include Aeromonas hydrophia and Pseudomonas fluorescens, which are likely brought in from sources outside of the tank.

This disease can be differentiated from others by the presence of protruding scales, without body bloat. Scale shedding may also be present, with scales sticking out at a noticeably awkward angle.

Treatments for Scale Shedding Disease include; isolating affected fish from the primary tank, antibiotics such as tetracycline or chloromycetin in food, and monitoring for improvement.


Goldfish can grow back their scales but under certain circumstances. Missing scales lost due to damage may regrow back, but smaller. Those lost to severe fungal infection or disease may never truly regrow.

The amount of time that it takes for new scales to grow can vary between breeds, taking anywhere from a few weeks to several months to see results.

Can Goldfish Live Without Their Scales?

Goldfish Swimming in a Tank
Goldfish Swimming in a Tank

Again, the answer is yes, but with some limits.

Fish who naturally have scales but have been damaged to the point of having no scales remaining, may have a difficult time surviving.

Without their protective outer layer, their skin is easily damaged which can lead to further injury and danger of infection.

Fish Health and You

When creating an underwater world for your healthy fish to inhabit, there are some simple things to keep in mind.

Monitoring the water quality on a consistent basis, keeping clean equipment, and introducing new fish and accessories at a safe pace go a long way towards keeping the habitat clean and healthy.

Thanks for reading this article, I hope it was helpful in your aquarium adventure and wish you good luck! If you found this information useful, please feel free to share it with friends, family, and any fish fanatic you may know.


  • “Disease.” Animal World. animal-world.com/encyclo/fresh/information/Diseases.htm. Accessed 18 Oct. 2021.
  • Liu, Li & Chu, H. Pseudomonas fluorescens: Identification of fur-regulated proteins and evaluation of their contribution to pathogenesis. Diseases of aquatic organisms. Retrieved Nov 16, 2021, from https://pubmed.ncbi.nlm.nih.gov/26119301/.
  • Marks, J.W. (2021, June 3). Medical definition of dropsy. MedicineNet. Retrieved Nov 16, 2021, from https://www.medicinenet.com/dropsy/definition.htm
  • Purcell, Maureen. “Icthyobodo.” USGS. usgs.gov/labs/wfrc-fhp/science/icthyobodo-fhp. Accessed 19 Oct. 2021.
  • Research Gate. https://www.researchgate.net/post/What_is_the_reason_for_scale_loss_in_trouts_Does_anyone_have_any_experience_idea_on_that. Accessed 18 Oct. 2021.
  • Skomal, Gregory. Saltwater Aquariums for Dummies. New York City, Hungry Minds, Inc. 2002.
  • The Center for Food Security and Public Health. Iowa State University. Viral Hemorrhagic Septicemia. 2009.
  • White, R. (1991). Diagnosis of Aeromona Hydrophila Infection in Fish. Aeromonas hydrophila infection in fish. Retrieved November 16, 2021, from https://www.addl.purdue.edu/newsletters/1991/aeromonas.shtml
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