Why Does My Goldfish Have Black Spots? {Cause & Treatment}

Are you noticing dark spots on the skin of your goldfish? Why does my goldfish have black spots?

Do you think the black spot is a symptom of a disease or do you think the black spots are only a result of coloration?

Learn more about the dark spots on your goldfish in this article.

Why Does My Goldfish Have Black Spots?

  1. Black spots on a goldfish body are mostly a result of parasitic infestation.
  2. Mild infestation cases will cause a sparse appearance of the spot at different parts of the goldfish body.
  3. Serious infestation usually causes more occurrences of the spot on the fish body.

Allow me to explain these three points and more with the details below:

Black Spots on Goldfish

Will Black Spots on Goldfish Go Away?

Goldfish spots going away depends on the action you take concerning the situation. If you do not take any action regarding the situation, the black spots will remain, or even become more than it was before.

After treating the cause of the spots on the fish, your fish may or may not retain its former color. Your goldfish retaining its color after treatment depends on the cause of the spots.

If the spots result from a genetic condition, the spot will not go away but remain there forever. If it results from infections or water chemistry, the fish will recover from the spot and regain its normal color.

Are Black Spots Caused By Ammonia Poisoning?

If the black spot is a result of ammonia poisoning, you will have to worry more about your fish’s health than the black spot.Ammonia poisoning is not good for your goldfish and can be fatal.

You do not have to worry much as, most times, the spot will vanish, and the goldfish will return to its normal state.


  • one of the causes of black spots in your goldfish
  • burns the fish skin causing black spots to appear
  • results from uneaten food, fish waste, plant debris, etc., in the tank.

When the ammonia level starts reducing:

  • the skin begins to heal and starts having black patches
  • the skin will go back to its previous state

You have to make sure you control the ammonia level in the water for your goldfish to ensure good health.

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Causes of Black Spots on Goldfish

Several factors can cause your goldfish to have black spots. The cause of the spot determines how severe the spots will be. Here are two causes of black spots in a goldfish.

1. Injuries

Injuries can also cause your goldfish to have black spots on its body. It occurs when your goldfish bruises its skin against something. As the skin starts to heal, black patches start to appear due to the healing process.

2. Parasitic infestation

Parasitic infestation is another cause of black spots in your goldfish. If you look into most black spots in fish, it is a result of parasitic infestation.

The parasite (dark in color) burrows into the fish’s skin, causing irritating black spots on its skin. The parasite also lays its eggs in the skin of the goldfish, making matters worse.

How Do You Treat Black Spot on Goldfish?

Treating black spots in your goldfish requires a different approach, depending on the cause of the spots.

If the spot is a result of a genetic condition:

  • you might have little control over it. 

If the spots have other causes:

  • you will have to take steps to treat the goldfish.

If the spot results from an ammonia spike in the water

  • you will have to take proper actions on the water.
  • increase the level of oxygen concentration
  • add organic carbon into the water.

Ammonia poisoning burns the fish skin, but these burns are not visible, so you might be able to see it. The black spots appear when the burns start healing. You have to control the level of ammonia in your pond for the good appearance of your goldfish.

Goldfish Parasites

The most common source of black spots on goldfish is parasitic infestations. To treat the goldfish of this infestation, you will have to get rid of the parasites themselves.

The parasites and their eggs burrow under the skin of the fish, causing black spots to appear.

You also have to get rid of the eggs and parasites to free your goldfish. Fish get the parasitic fluke disease from infected water snails or even bird droppings.

You will have to remove the snails from the pond and also prevent fish-eating birds from getting to the pond.

Steps to Take to Prevent Black Spots on Goldfish

Prevention is better than cure, they always say. It is better to prevent your goldfish from having black spots than treating it from having black spots. Here are steps for the prevention of black spots in your goldfish;

  1. Perform a regular check on the ammonia level of the water.
  2. Try not to overfeed your goldfish.
  3. Remove waste food from the water immediately after feeding.
  4. Perform routine cleaning of the tank or pond.
  5. Get rid of every snail in the tank or pond.
  6. Prevent fish-eating birds from getting to the pond or tank.

If you can take these steps, your fish will be far from having black spots. They will be able to remain colorful without any blemish on their skin.


The black spot in fish is not very common unless the fish is in outdoor ponds. Removing snails and preventing birds from getting into the pond will break the life cycle of the parasites. Your goldfish will also recover over time.

Goldfish have black spots on their body mainly due to parasitic infestation. They can also develop these black spots due to genetic conditions, ammonia poisoning, etc. You have to know the cause of the black spots before you can treat them.


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John Brandon

John has kept fish all his life (since he was about 5). He started with keeping guppies and fell in love with fish keeping almost straight away. That was 40 odd years ago. These days John still keeps fish and currently has two large tanks where he keeps many different types of fish such as Angelfish, Neon Tetras, Goldfish, Guppies and many more.