Why Is My Goldfish Turning Black? (Answered)

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Complete Guide On Goldfish Turning Black

Recently, I visited a friend. He had acquired a new hobby of fish keeping, and since I had been doing it for quite a while, he wanted me to come over and look at his collection.

I was just looking around and seeing all the beautiful fish he had got for his aquarium when suddenly I saw something.

He had some goldfish in one tank, and most of those goldfish were turning black. I immediately asked if he had noticed that his goldfish were turning, and if so, then why hadn’t he done anything about it?

To my surprise, he didn’t know that goldfish turning black is bad; shockingly, many people don’t know this either. So today, I have decided that I will be educating you guys about the reasons why goldfish turn black and what should be done when they start turning black, and if it is possible to get their original color back.

So stay with me till the end, and you will learn how to take care of your dear goldfish.

Why Is My Goldfish Turning Black?

There can be many reasons why your goldfish is turning black. This can be caused by either bad water quality due to your goldfish being sick or maybe because your goldfish was injured and is now recovering.

Stressed Out Fish

Stress can be a significant reason why goldfish change their color. Goldfish love to live in a peaceful and harmonious environment, and if there’s chaos in their surroundings, they get stressed out.

image of goldfish turning black a bit

If the goldfish are stressed out, there is a high chance that they will eat properly, and this will cause stress and malnutrition to their organs. This will cause them to get sick and start turning black.

Dangerous Ammonia

I can not stress this enough, but a clean tank will lead to healthy fish. One of the biggest causes of goldfish turning black is too much ammonia in the tank. But how can a clean tank prevent ammonia production?

Signs of Ammonia poisoning in fish tank
Credits: Pet Mart

Ammonia is produced when waste is decayed inside the fish tank. This decay not only produces ammonia but also provides reproduction sites for many harmful bacteria. Which later on will affect the health of your goldfish.


While most of the time, goldfish turning black is a bad sign, there are cases where it isn’t. If you have a crossbred goldfish, there are chances that it will change colors as it transitions from a baby to an adult.

image of some goldfishes having black spots

Although it is not necessary that the goldfish will always turn black, but in most cases, it does. In this case, the change in color is very slow and gradual. These changes will occur over the first one or two years of their lives.


Although this is a rare case, there is a disease that causes goldfish to turn black. This is known as black spot disease. And as the name of the disease already suggests, this disease causes goldfish to develop black spots all over their bodies.

image of goldfish black spot disease

This disease is more common among goldfish that live in a pond than those that live in an aquarium.

Healing From Injury

As I said earlier, if a fish is stressed out, it will cause your goldfish to change color. Injuries can put your goldfish under a lot of stress. During this time, they suffer from pain, and this causes a reduction in their appetite.

Due to this, while healing from an injury, there are chances that the fish is not getting enough nutrients and might start turning black for this reason.


Overfeeding your goldfish can cause health problems for them and make them prone to many diseases. Due to overfeeding, these fish get sluggish and are not able to swim properly, and thus their organs start to get weak.

image of goldfish eating food

This causes different health issues for your goldfish, and they start to lose their original color and start to turn black. This is why it is suggested to only feed your goldfish 2 or 3 times a day.

Light Exposure

Light is an absolutely important element for the goldfish to develop and maintain their color. They require around 12 to 13 hours of light daily for this purpose.

If goldfish do not get sufficient light, they stop producing chemicals that maintain their color. As a result, they either start to turn black or white, depending on which one is the dominant one in their genes.

How To Prevent Your Goldfish From Turning Black?

Now that I have discussed the major causes of your goldfish turning black and changing their color, it is important that I tell you what measures you should take in order to stop your goldfish from turning black.

#1- By Removing Snails

Snails are one of the major reasons why goldfish get black spot disease. These infected snails release parasites into the water that cause the fish to catch this disease.

image of an aquarium snail

In order to protect your goldfish from this disease, it is important to remove snails from the water. This will break the cycle of parasites and will give your goldfish a chance to heal from it.

#2- Avoid Aggressive Tank Mates

As I mentioned earlier, goldfish like to live in a peaceful and harmonious environment, and if there is anything that causes disturbance and chaos in their environment, these fish get stressed and become sick.

Aggressive tank mates are the reason for the chaos in fish tanks. In order to keep your goldfish relaxed, make sure that you remove and separate any fish that cause chaos in the tank.

#3- By Maintaining Good Water Quality

Clean and filtered water that is free of any harmful chemicals and toxins is very important for the healthy growth of your fish. Make sure that the ammonia levels of your tanks are under control and that there is no decaying material in the tank.

image of aquarium in black background

Make sure that the water in your tank is changed on a regular basis, and make sure that the filters are also cleaned and do not accumulate any harmful bacteria in them.

#4- Keep Some Lighting Around Your Tank

Lighting, be it natural sunlight or artificial light, is very important for your goldfish to develop and maintain their color.

Make sure your tank is kept in a well-lit area that receives an ample amount of sunlight during the day. This way, your goldfish can develop their natural color properly and can avoid becoming black or white.

#5- Monitor Fish Temperament

If the change in color of your goldfish is caused by any disease or due to ammoinia poisoning, your fish will show signs of discomfort.

If you see your fish struggling and becoming sluggish or trying to rub itself against other objects, there are high chances that there is some problem that needs to be taken care of.

Goldfish are also very peaceful, so if you see that they are acting out and being aggressive, that can also be a sign that there is some issue with them that needs to be fixed.

Will Black Spots on Goldfish Go Away?

If these black spots are caused by ammonia poisoning or due to black spot disease, there is high chance that they will go away with the passage of time. Just make sure that your fish is at its peak health and that there aren’t any parasites or excess ammonia in the water.

image of ranchu goldfish in an aquarium

But if these black spots are caused by genetic reasons, then your goldfish will remain this way. But this should not be a problem, as this will in no way affect the health of your goldfish.

Why Is My Goldfish Not Swimming After Turning Black?

As I explained earlier, the goldfish usually frash turning black because of either ammonia poisonong or due to some health issues.

goldfish turning black

If your goldfish is also turning black due to this, there are chances that the damage to your goldfish has gotten worse and has now started affecting their internal organs.

Due to this internal organ damage, the goldfish start to conserve their energy and become sluggish. And for that reason, they either swim very little or just stop swimming at all and stay put in one place.

Final Verdict:

To conclude the topic of why your fish is turning black, I would say, keep a close eye on your fish. Make sure they have a healthy and clean living environment that is free of any chaos and stress.

Keep a close eye on the ammonia levels of your fish tank and regularly clean up your tank and change its water.

But don’t be too stressed if all the conditions are right and your fish is healthy and has still started to turn black. It can be caused for genetic reasons as well, and in that case, this color change will not affect your goldfish in any way.

Frequently Asked Questions

#1 – Can Goldfish Recover From Ammonia Poisoning?

Your goldfish can recover from ammonia poisoning and will be able to get their original color back if the ammonia poisoning is identified and stopped at an early stage. Otherwise, your fish may not recover.

#2 – Can Goldfish Change Color From Black To Gold?

It depends on the reasons why it turned black in the first place. If it is caused by ammonia poisoning or any disease, then it may turn gold again. If the change is genetic, then it will not.

#3 – Can A Goldfish Get Its Color Back?

If the color change is caused by ammonia poisoning or any disease, it can be reversed. If it is caused due to the fish’s genetics, then it can’t.

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  • Since 2009 I've been writing on different media portals about fishing. Here on this website, it's time to share those experiences I've witnessed in my entire life so far. Let me help you get the best stuff you need while fishing.