How To Treat Red Spots On Goldfish {Red Pest Disease}

Has your goldfish got red spots on them? Are you wondering how to treat red spots on goldfish?

The red spots are red pest disease , Treatment is needed to get rid of them.

In this article I will show you how to identify red pest disease in your goldfish and what you should do to treat it.

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How To Treat Red Spots On Goldfish

Red spots on a goldfish can indicate a variety of health issues, and the appropriate treatment will depend on the underlying cause. Here are some common causes of red spots on goldfish and their potential treatments:

  • Bacterial Infection: Bacterial infections can cause red spots or ulcers on a goldfish’s body. Treatment often involves improving water quality through regular water changes, maintaining appropriate temperature and pH levels, and using aquarium salt or antibacterial medications as prescribed by a veterinarian.
  • Parasitic Infection: Certain parasites, such as ich or flukes, can cause red spots or irritation on a goldfish’s body. Treatment may involve using anti-parasitic medications specifically designed for fish. Quarantining affected fish and disinfecting the tank may also be necessary.
  • Fungal Infection: Fungal infections can lead to red spots or patches on a goldfish’s body. Treatment may involve using antifungal medications and maintaining clean water conditions. It is important to address any underlying causes of stress that may have contributed to the infection.
  • Poor Water Quality: Red spots can also be a result of poor water quality, which can irritate a goldfish’s skin. Ensure appropriate filtration, regular water changes, and maintain proper temperature and pH levels in the tank.
  • Physical Injury: Goldfish may develop red spots due to physical injuries, such as abrasions or bites. Keep the water clean to prevent infection, and provide a stress-free environment for the fish to aid in healing.

It is crucial to properly identify the underlying cause of the red spots before starting treatment.

Goldfish Red Pest Disease Treatment

What Is Red Pest Disease?

Red pest disease is a disease that significantly affects the general welfare of fish. The condition causes red spots on fins and tails of fish, thus allowing it to appear like the fish is bleeding, but the disease is not contagious.

The bloody streak does not have to appear in all the parts before you know it is red pest disease. It sometimes affects only either the body or fins.

The causative bacteria agent of this disease is an opportunistic bacterium and often gets a hold on weakened fish.

These streaks could proceed to become ulceration, and it can consequently lead to fin and tail rot. In severe cases, the decay can cause tails and fins to fall off entirely.

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Is Red Pest Disease Terminal

Red Pest Disease, also known as Lymphocystis, is a viral infection that commonly affects fish. While it can cause unsightly red or pinkish growths or nodules on the fish’s body, fins, or gills, it is typically not considered a terminal disease.

Lymphocystis is a self-limiting disease, meaning it often resolves on its own over time as the fish’s immune system fights off the virus. However, the duration of the infection can vary, and it may take several weeks or even months for the growths to disappear completely.

In most cases, Lymphocystis does not cause significant harm to the fish unless the growths become excessive or affect essential functions like swimming or feeding. The main concern with Lymphocystis is aesthetic, as the growths can be unsightly.

What Are The Red Spots On My Goldfish?

The red spots on a goldfish are a sign that there are external parasites on your fish.  The red spots are rashes that have developed from the irritation.

If the red spots are large enough to see with the eye then the condition is quite serious.

If your goldfish is turning black take a look at this article to find out why.

What Causes Red Pest Disease In Goldfish

Red spot disease in goldfish is mostly as a result of bacterial infection and poor water quality. In most cases, these two factors can complement each other to make goldfish susceptible.

Ordinarily, these causative bacteria cannot get hold of healthy fishes, and poor water quality can affect the health of the fish.

Red pest disease can be a result of infection from a bacterium known as Bacterium cyprinid, which is an opportunistic organism that cannot affect healthy fishes.

Bacterium cyprinid is a pathogenic bacterium common in aquariums, ponds, and other aquatic environments.’

Is Red Spot Disease a Fungus?

Yes. It can be caused by a fungus known as Aphanomyces invadans. It is typical for showing red lesions or bleeding streaks; it can result in deep ulcers.

Aside from the fact that this fungus can cause red spot disease on its own, it can also make room for secondary bacterial infection.

Also, non-living factors can be responsible for the red spot disease in fish such as:

  • poor water conditions
  • poor feeding
  • high level of ammonia
  • high nitrate level

Is Red Pest Disease Contagious In Goldfish?

Red pest disease itself will not spread from one goldfish to another, The disease is spread through poor water conditions, so if one of your fish has the disease, your other goldfish will most likely also get the disease.

Red pest disease will attack and infect goldfish that have weak immune systems.  If your fish are in poor water conditions it is only a matter of time before they will get poorly.

The red pest disease will come from some bad bacteria in your tank, check for the source such as

  • Dead Fish
  • Rotten Food
  • Blocked / Dirty Filter
  • High or Low Levels of pH and Ammonia

Recommended Antibiotics For Treatment

There are a variety of antibiotics that can be active as internal medication for red spot disease.

  • Tetracycline
  • Chloromycetin [chloramphenicol]

These are the two most common antibiotics that are effective in the treatment of red spot disease. The concentration of these antibiotics is also crucial in determining how effective it will work.

If for some reason, the fish fails to ingest the food, you can add the antibiotics directly into the tank. You can add 10mg of antibiotics per 1 liter of water. This method is, however, not as effective as mixing antibiotics with fish food.

You can also clean the tank with fish disinfectants like:

  • acriflavine [trypaflavine] 
  • monacolin [mono aminoacridine]

You should, however, discontinue the use of antibiotics if the fish are not comfortable with it.


Red spot disease in goldfish can be a significant cause of concern to aquarium owners. It is life-threatening and can result in the overall deterioration of fish life.

Nevertheless, this disease can remain under check by ensuring that your fish live under perfect conditions. You can also get rid of this disease with the simple use of antibiotics.


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Hello, I'm Jason. I'm the guy behind I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.