Why is My Goldfish Turning Black & What Should I Do? (2022)

Once you get pets, it doesn’t take long before they turn into one of the most important and precious things in your life – no matter which animal you have.

And that includes your goldfish.

If you notice that your goldfish is turning black, it might be very worrisome for you. You may start wondering, “Why is this happening?”, “Is it something bad?”, “Should I go to the vet?” and the list can go on and on. After all, watching your gorgeous goldfish turn black is a scary sight.

But you don’t need to panic.

Let’s take a look at the reasons why this may be happening, what you can do about it, and whether it can go back to its normal color.

goldfish turning black

Should you be concerned?

When you see your goldfish turning black, the first thing that probably comes to your mind is that something is definitely wrong.

And while it is completely understandable that you may think that way, it’s actually not always a life-threatening or dangerous situation. And sometimes, it is even natural for the fish to change color.

But don’t take your sigh of relief yet. You need to first take a closer look as to whether it is serious or not. In some cases, your goldfish might be suffering, and you might need to take a step as soon as possible.

Why is it happening, and what can you do?

Serious or not serious, there are some common factors responsible for the color change.

Here are some of the most common reasons it could happen, and what you should do in each specific case.

Suffering from ammonia poisoning

The most prevalent and harmful reason for the color change is ammonia poisoning, which occurs due to high levels of ammonia in your tank. And this is not only common for goldfish; any light-colored fish species can experience this.

If you don’t clean out the mess and extra food from your tank regularly, you allow toxic ammonia to be released into the water, which will harm your goldfish. This is why caring for your fish tank is essential.

Ammonia is lethal to fish, as it poisons them and kills them quickly if you don’t take action fast enough. Black fins are an indication of high ammonia levels. In high concentration, the chemical essentially burns your goldfish’s skin and gills, thus killing the fish.

But before you start to panic, you should know that your goldfish turning black is an indication that it is healing. You didn’t expect that, right?

Since it is impossible to see ammonia in the water, you can’t tell if your fish is burning. But once you see the black patches, it most likely means that the level is safe.

But it is better to be safe than sorry. You need to stop assuming and make a routine of cleaning your tank more often. Make a habit of checking the water regularly to make sure that the ammonia level does not exceed 0 parts per million (PPM), because even 2 PPM can be fatal for your fish.

Change the water out more often, and if possible change around 20% of the water every week. Make sure your filtration system works properly and remove dead plants from the tank.

This can also happen if you overfeed your fish and then don’t clean out the leftover food, as it will contaminate the water and disrupt the filtration efficiency. Make sure to remove any leftover food as soon as possible.

If you have sick and stressed fish, make sure to move them to another tank, as this offloads a lot of ammonia and can cause further problems for the entire tank.

ammonia poisoning

Blending into the environment

The previous reason may have been too much for you to take in. So let’s move on to a relatively harmless reason now…

Since goldfish are adaptable creatures, they tend to change to black to blend in. So if you just got a goldfish and put it in a tank with a dark background or wallpaper, don’t be surprised or worried – it is just your fish blending in.

Fish contain different cells in their skin, and within them, there are pigment cells that produce a dark pigment known as melanin. This is what contributes to turning the tail of your goldfish black!

If you place your fish in a dark environment, it will blend in as a camouflage mechanism. The cells will produce more melanin and turn it black, so it can hide from its predators. This may appear either as patches around the tail, fins, or tails or cover its whole body. But you don’t need to worry as it is completely harmless.

However, if you are not a fan of the black color and want the fun bright-colored fish back, change the surrounding or the background into a lighter color, and the pigment will wear out and go back to gold.

Black Spot disease

Although the black spot disease is relatively rare, it is still a possibility.

It is only likely that your goldfish suffers from black spot disease if it is in a pond or a tank that contains snails.

But what is a black spot disease? It is a parasitic infection that causes black spots on fish – pretty self-explanatory, right?

Fish usually catch it from snails as the lifecycle of parasites involves being passed in bird droppings, reaching the water, infecting the snails, and further infecting the fish.

So, if you have snails in the tank, there’s a high possibility that your fish is infected with the disease. You can also determine if the black spot disease is responsible for the black spots by checking if the goldfish is flicking its body and trying to rub against items near it. This is because the spots tend to be very itchy, and, like us all, the fish just want some relief.

If you believe that the black spots on your fish are due to this disease, you should first remove the snails from the tank to break the lifecycle of the parasite. You will not see immediate recovery for the fish, but eventually and gradually, it will recover.

However, since the probability of your goldfish turning black due to this disease is very low (unless your fish is in a pond), we suggest considering other options before you reach a conclusion and start the treatment.

Black Spot disease goldfish


It might be unusual for you to think that goldfish can be black – the name literally says ‘gold’ fish, so it must be gold, right?

Not quite. Although it is indeed rare, there are possibilities!

Many goldfish species are blended breeds. They are not carefully bred, which is why they can’t maintain certain qualities, which also include coloration. So ‘mixed breed’ goldfish species change their coloring, and it isn’t definite that they will stick to one.

These fish change colors when they transition to the adult stage from the juvenile stage – although not all of them do so. This occurs within the first two years, as that is usually when genetic changes take place. You might not even notice it because the change is so slow!

Luckily, these changes are not dangerous or life-threatening for your goldfish, so you don’t have anything to worry about!


Goldfish respond to stress in their lives, just in a different way than us humans do. This is why you might start seeing black spots all over their fins and scales.

If you have changed the environment of your goldfish, it is likely that it has caused stress or illness. This may also be the case if you have added a new species of fish into your tank.

So, what should you do about it?

Watch your goldfish closely to figure out if it has any illness. But keep in mind that if the black patches are due to stress without other factors, you don’t have to do anything. Your goldfish will go back to its original gold color naturally over time as it relaxes!

Can it turn back to normal?

The answer to this question depends on the cause of the color change.

If it is genetic, your goldfish will likely remain that color for the rest of its life. We understand that you wanted a goldfish, but possibilities are always there. The good thing is it isn’t harmful to the fish.

If it is due to stress, as mentioned before, the goldfish will regain its natural bright colors back naturally over time.

However, if the changes are due to ammonia poisoning, the more important concern is whether your goldfish will make it or not. Ammonia poisoning for a goldfish is a serious issue, and in many cases it is fatal. But that does not mean that you should give up any hope of your precious pet recovering. There are cases where they recover fully. Remember: black patches are a sign that the chemical burns on your goldfish are healing!

Just keep monitoring your fish’s behavior very carefully, and if you see it swimming normally and being lively, then your fish can most likely make it.

As for the coloration going back to normal, you will have to be patient as it will take time, but eventually, the spots will fade away.

How to prevent it from happening in the future?

Taking preventive measures is essential for keeping something like this from occurring again – unless it is genetic!

Here are some ways you can prevent it from happening:

  1. Keep a strict check on the ammonia levels in your tank
  2. Clean the tank regularly
  3. Get rid of waste food immediately and avoid overfeeding your fish
  4. Do not keep snails in the same tank as your goldfish
  5. Avoid using dark backgrounds in your tank

preventive measures in aquarium

Frequently Asked Questions:

Will black spots on goldfish go away?

This depends on the cause of the black spots. If it is genetic, then the black spots will stay. However, if it is due to any other cause, the black spots will likely go away – but patience is the key!

What are the signs of a dying goldfish?

These are different symptoms of a dying goldfish, such as:

  1. Loss of appetite
  2. Milky white areas around its tails or fins
  3. Folded or torn fins
  4. Erratic swimming motions
  5. Gasping for air
  6. Blowing bubbles from rapidly moving gills
  7. Unusual eye appearance
  8. Loss of weight
  9. Prolonged immobility and lethargy

It is often difficult to tell what is wrong with your goldfish. Therefore, if you feel that something is really wrong with your goldfish, you should first talk to a vet.

Do goldfish stay black?

Your goldfish will not necessarily stay black forever. Not all color changes are permanent; it depends on the cause.

If it is due to ammonia, stress, disease, or a dark environment, your fish can go back to its original color once you fix the problem. However, if it occurs due to genetics, it will likely stay black forever.

Why did my goldfish change color?

The change in your goldfish color may be caused by a variety of factors that include genetics, aging, water quality, diet, and in some cases, an illness or disease.

Closing Thoughts

Now that you have a good amount of knowledge regarding your goldfish turning black, you know what you need to do differently.

We know you love your pet, and with these tips in mind, you can make sure they thrive well!