Goldfish are the most adorable fish that every fish keeper loves to keep. 

But one of the main problems is that goldfish can affect any disease without proper care. Here, The goldfish have fins turning black problem and today we will walk through different reasons and solutions for the goldfish fins getting black.

The goldfish fins turning black was due to various reasons such as high ammonia, water temperature, poor water condition, and aquarium size being too small. The primary reason is the high ammonia in the tank and lack of care.

Goldfish Fins Turning Black

In my experience, I have tried a lot of ways to reduce the goldfish fins turning black problem. So I’ll be sharing the different ways to solve the problem as you can try this and save the goldfish.

Goldfish Overview

Goldfish Fins Turning Black
  • Ammonia <0.1 ppm
  • Nitrite <0.2 ppm
  • pH Level 6.5-7.5
  • KH 70-140 ppm
  • GH 150 ppm
  • Temperature 20-24°C

Why is my fish’s fin turning black?

Goldfish Fins Turning Black

The goldfish have fins turning black problems and it was due to various reasons such as High ammonia, poor water condition, natural fin color change, and water temperature.

These are the main reason for the goldfish fins turning black problems and many people and experts have suggested different ways to treat them.

Many peoples are not caring the goldfish due to lack of time. You need to spend a little time on fish because they can reduce the frustration in your mind. There are a lot of benefits while fish keeping and the majority of people don’t know about them.

Fish can reduce stress because studies have proven it. In my experience, I have faced a lot of problems as a businessman but setting up a fish tank and spending some time with them have reduced my stress and frustrations.

As an experiment, you can check and test it.

What is the symptom of goldfish turning black?

Goldfish Fins Turning Black

The main symptom of the goldfish turning black is black spots on the body parts. You can see small black spots on the body parts. It was mainly due to the high ammonia in the tank.

The goldfish will heal the ammonia-affected parts and when the parts get healed, you can see black shades or black spots on the healed parts.

So you need to test the ammonia twice a week and clean the water once a week to reduce the ammonia spread in the tank.

Let’s look at the main reasons in depth.

Reasons for goldfish fins turning black

Goldfish Fins Turning Black

These are the main reason goldfish fins turn black. But you can easily fix these issues and care for them to heal. So let’s look more in-depth at the reasons.

Natural fin color changes

Goldfish Fins Turning Black

When the water becomes dark, the goldfish with dark skin pigments start showing up. The goldfish have cells in their scales that produce melanin and causes black stain on the skin.

It was changed naturally and it will start spreading around the body. So you need to provide the goldfish good care and need to change the water once a week.

Sometimes the goldfish may lose color due to stress. If the fish acquired any infection or stress, you need to reduce the stress and infection of the fish.

Mainly the goldfish changes color when they heal the infected parts of the body. You can see the difference in the healed parts. 

Due to high ammonia

Goldfish Fins Turning Black

Another reason for the goldfish fin turning black is due to high ammonia. Ammonia is formed when the uneaten feed in the aquarium decomposes.

If the ammonia content is high, you need to change the water as soon as possible. Otherwise, ammonia will start affecting the fish’s body parts.

Ammonia poison is very hard to cure.

So you need to be very careful about it. The ammonia can cause stress, to the gills, fins, and internal parts of the fish. That can lead to the death of fish too.

If you see the ammonia increasing in your tank, Reduce the number of feeds and use a filter for cleaning the water.

If the ammonia increase in the tank, the fish will have swim bladder disorder and I’ve created a detailed post about swim bladder disorder.

Aquarium too small

Goldfish Fins Turning Black

If the aquarium size is too small, the goldfish will be congested in a small area. So there will be a change for increasing the ammonia levels and stress.

Also, If the fish start fighting or chasing each other, there will be a chance of body damage that leads to many problems.

Water Temperature

Goldfish Fins Turning Black

Water temperature is the main important of fish living. 

Sudden changes in the temperature will affect the health condition of the fish. They may also get stressed.

You need to check the water temperature every day. The recommended water temperature for goldfish is 20-24 °C.

 Make sure that the water temperature is correct before adding the fish.

Poor water conditioner

Goldfish Fins Turning Black

The last reason for goldfish fins turning black is poor water conditions. The goldfish fins can turn black in color when poor water conditions which means the dirty water has high ammonia and nitrite.

This will make the fish fins turning to black in the darkness. So you need to clean the water once a week and clean the tank in a month. Use the aquarium filter and air pump for generating oxygen content and cleaning the tank.

Do goldfish turn black when stressed?

The goldfish may turn the color to black when they are stressed because stress is an illness due to poor water conditions.

The goldfish may regain color when they reduce stress. So you need to care about the water parameters such as ph level, water temperature, etc.

Can fish heal from fin turning black?

When you overfeed the fishes, the waste food becomes decomposed and lead to ammonia spread in the tank. It will affect the fish’s body parts such as fins, gills, tails, etc.

So the fish will heal themselves and the healed parts will get black shades or spots. That’s why fish healing parts become black color. 


How do you treat goldfish fins turning black?

It was mainly due high level of ammonia in the tank. So you need to decrease the ammonia in the tank.

The best way to reduce the ammonia in the tank is to clean the water.

You need to remove 80% water from the tank and refill it with fresh water. So you need to be careful about the water parameter when you put the fish.

Another way to reduce ammonia is by using ammonia remover. You can use ammonia remover to reduce the ammonia from the tank. You can buy ammonia remover from amazon.

If you see the black color on the fins, Separate the fish to another tank with fresh water and filtration. Also old tanks after removing the fish, otherwise they will get infected due to high ammonia.

In the separate tank, you need to change 50% of the water regularly to dilute the ammonia. Also, add chemical filtration to the aquarium to remove the ammonia.

Wrapping up

Now you know the way to treat the goldfish when they have fins color changing to black with reasons. You can treat the fish carefully and remove the ammonia from the tank.

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