Do Fish Shed Their Scales as They Grow?

There are many instances when fish began shedding their scales. Most people compare fish to snakes and they think fish shedding their scales is all part of a normal growth behavior; but in reality, it is not.

Do fish shed their scales as they grow? Definitely not! Fish would not grow if it is losing its scales. These scales have to be replaced or at least repaired in order for the fish to grow. 

The scales of the fish mimic the qualities of the skin in humans. Hence the scales of the fish grow more as they get older.

Goldfish losing scales (Video)

Is it not normal for fish to shed their scales?

The amount of scales a fish has is directly proportional to its age. Just like the rings of a tree, the scales of the fish help in determining its age. This method helps experts guess the age of prehistoric fish fossils.

Why is my fish shedding its scales?

Scale loss can be due to many reasons which include:

  • Physical damage
  • Abrasions
  • Infection
  • Some other disease

Scale shedding disease

Scale shedding (which is also called infectious protrusion) is a prevalent disease among aquamarine fish. It is caused by dangerous bacteria such as Pseudomonas fluorescens and Aeromonas punctate. If this condition is left untreated, it becomes relatively fatal.

These bacteria can be found in nature and are brought into the aquaria from natural reservoirs. This disease is spread when an infected fish is placed in the same fish tank with other healthy fish and is not quarantined in advance.

The disease can also be introduced into the fish tank via gravel, water, and plants from infected tanks. Another method of transmission is from fish tanks and other equipment used in these tanks.


The symptoms of this disease include

  • Scale shedding
  • Scale raising

In the early stages, the fish looks healthy, but some protruding scales can be witnessed. As the disease develops, the scales begin to stick up all over the body of the infected fish. This is due to the formation of small bubbles full of serous fluid or pustules.

These pustules form in places under the skin where the scales are attached to the body of the fish, and so this leads to loss of scales. Due to the loss of scales, the formation of pustules and the protrusion of scale, the young fish have difficulty breathing as they use dermal respiration at that stage rather than their gill apparatus for the exchange of gases.

These specific symptoms do not always hint towards this disease. Sometimes, the scale protrusion is caused by bacteria such as Ichthyosporidium or Mycobacteriosis. To have a reliable diagnosis, it is vital to make an examination of the scales as well as the tissue that surrounds it.

In some cases, it might also be essential to carry out an intensive examination of the inoculation of the viscera (the liver, kidneys, spleen and the heart) and the hypoderm.


It should be kept in mind that this disease can only be treated if it is caught in the early stages when the scales begin to stick up in patches.

  • Basic Violet K can be made use of in treating the fish in separate tanks
  • Antibiotics Bicillim-5, Sulfanilamide, and Biomycin can also be used

The fish that showcase very extensive scale protrusion should not be kept any longer as they are beyond the stage of getting cured. The fish should be disposed of; and the aquarium,  the equipment, and the fishing tackle should be disinfected.

5 percent of Sulphuric acid, Hydrochloric acid or Chloramine solution should be used to clean these items. The gravel itself should be boiled or tempered as a means of disinfection. The plants, on the other hand, should be treated with a Bicillin-5 solution.

Related questions

Can an encounter with hard objects cause scale loss in fish? Yes, this is quite common; fish tend to brush up against hard objects especially during the breeding season. This causes them to lose a number of scales. It is best to decorate your fish tank with objects that do not have sharp edges and rough surfaces.

Does the Pleco fish harm the scales of the Goldfish? Yes, it does. The Pleco fish is known to suck the slime coat off the goldfish and this results in scale loss as the goldfish loses its protective covering. The Pleco fish can also attack the goldfish which can lead to their tail splitting.

Does adding salt to the fish tank help protect the fish against infection? Salt helps to improve the quality of the water in the fish tank. It prevents the fish from contracting severe illnesses and helps the fish maintain its internal chemical balance despite being covered with wounds.


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1 thought on “Do Fish Shed Their Scales as They Grow?”

  1. Hi
    I have two angel fish both male unfortunately in the early stages they were inseparable now they fight. One of my angel fish which was silver with black markings and a orange cap now looks pink as most of its scales look to have disappeared along his body.
    My question is could this be due to them fighting? The other one has all his scales and when they fight they go for each others mouth is this normal and would it stop if I got two females


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