Why is my Goldfish Turning Black?

Everyone loves pets. Pets provide companionship to humans; the relationship is an adorable and strong one! Pet feeding plays a large role in formulating this relationship. As far as pet feeding is concerned, pet health should is a major concern too. Be it a dog or fish, health is significant for every pet. If you have a Goldfish as your pet, you should not only take care of its food but of its aquarium health as well. After all, we love our little water buddies!

Goldfish and Color Changes

Fishes are easy to take care of. They are easily found in stores and adapt to live in an aquarium. The shimmery gold color of a goldfish attracts the viewers, and readers, be amazed- this dazzling appearance results from thousands of years of selective breeding! However, this beautiful color may change at certain times. When a goldfish starts to turn black, you’ve got a problem!

Color changes to white are more common rather than black. Therefore, if your fish is turning black, you must remain vigilant because it can be dangerous. By general assumption, we can assume that there may be some unhealthy environment due to which the fish is suffering internally. Hence, you need to address this matter seriously. There are possibilities that a fish can change its color normally/naturally. So while this color change can be alarming, it does not always indicate something wrong with your fish. Either way, caution is a must.

Causes of Goldfish Turning Black:

There are many reasons why a goldfish is turning black. Let’s skim through a few! As we mentioned earlier, the black color change is rare in goldfishes. Consequently, you’ll need to consider all the causes to determine the main reason. The black color change is notoriously unstable in goldfish. Some of the main reasons for this change are mentioned below: 

Ammonia in the Tank 

Ammonia changes are by far the most common reason why goldfish flip black. Generally, the color change begins on the fins. Over time, it can get worse and move to the body. There, it’ll appear as small batches of black pores and skin that appear burnt. Ammonia is a toxic chemical that’s produced inside the fish aquarium. Most people don’t recognize it, but caring for fish in captivity is a constant struggle of stopping ammonia buildup in the tank! That’s the factor of the filtration and cycling system!

Fish produce ammonia through waste. Decaying plants and uneaten food can cause ammonia spikes too. Water modifications are efficient in getting rid of the chemical so that the issue can be resolved quickly. A powerful filtration system will assist, as well.

When the tank isn’t clean, ammonia tiers can upward jab very fast. Beware, this chemical can kill fish! To make matters worse, the tank doesn’t need a large amount of ammonia to be fatal. Even a small concentration of 2 components per million is sufficient to kill small fish like the goldfish. Ideally, your ammonia degrees have to be 0 PPM.

How Does Ammonia Motivate a Black Color Change?

Well, the chemical is, if truth be told, burning your goldfish’s skin. That’s how ammonia kills the fish. Higher concentrations burn the gills. All this happens while you stay unaware of your beloved fish’s suffering. You see, it’s not possible to see ammonia in the water. You can’t know when the chemical is burning your fish’s physique either.


Make sure to use your testing equipment and check the water. Readings north of 0 PPM should be considered dangerous. Make it your motto to conduct more frequent water changes. When changing the water, conduct a 20 percent water change. After changing the water, make sure your filter is operating correctly. Study your fish closely to ensure that they are healthy.


Now onto a more harmless cause. Some specimens of goldfish are prone to color changes. While a goldfish turning black is rare, it’s nonetheless possible! “Mixed breed” goldfish are the most likely to go through some adjustments in their lifetime. These are typically the more cost-effective goldfish you see in the market. They may also already have some coloration patterns on them. These fish now and then trade colors when they transition from the juvenile stage to the grownup stage. This occurs within the first 2 – 12 months. The change is slow, so you might no longer even be aware of it at first. The goldfish may also develop darker black patches on the body. This should be accompanied by some areas getting lighter too.

“Purebred” goldfish that comes from an official breeder can turn a bit black as well. However, the change is generally a lot more subtle. You would possibly see some black streaks increase on the fins or small dots of dark color. Whatever the case might be, a goldfish turning black due to genetics is nothing to worry about. It’s completely normal and doesn’t lead to any health problems or a shortened lifespan.


Goldfish turning black due to sickness is rare, but it’s nevertheless a possibility worth mentioning. The ailment we speak of is called black spot disease. This is some distance extra common in goldfish kept in ponds than those residing in enclosed aquariums. The factor can additionally plague fish in the wild. Many fishers stumble upon similar diseased fish.

What is Black Spot Disease? 

It’s a parasitic fluke disease. Fish trap it from infected water snails. They eat snails, and these snails can come to your aquarium too, and for that reason, you need to keep check of it. If you want to learn more about freshwater aquarium fish-eating snails, read through this blog too. 

Goldfish in ponds can also come upon the sickness if hen droppings make their way into the water. Black dot disease reflects various factors. They will develop literal spots on the body. Infestations can range quite a bit as well. In mild cases, you might see a couple of spots right here or there.

However, severe infestations can drastically cover the goldfish in black. If you suspect that that disorder is to blame, observe your goldfish’s behavior. The spots tend to be itchy, so fish will flick their bodies and strive to rub towards gadgets to get relief.


To deal with this disease, you must reduce snail populations from the environment. It takes time for goldfish to recover fully, but they will. While the disorder sounds awful, it’s viewed as much less risky, so there’s no need to panic. Again, black spot ailment is rare. Unless you have goldfish living in an outdoor pond, your chances of encountering it are meager. Make sure your aquarium is tidy of these snails so that your fish don’t fall sick.

Can goldfish Turn Back To Their Original Color?

Goldfish turning black may or may no longer continue their natural color. It all depends on the cause of this change and the prognosis. If the black coloration trade is genetic, your fish will stay that way for the relaxation of its life! While the trade might also not be what you wished for, it won’t affect your fish’s fitness or its quality of lifestyle in any way. If your goldfish turned black because of ammonia poisoning, there’s reason to worry. The prognosis for ammonia poisoning is no longer available. In many cases, it’s a fatal issue. However, it is not hopeless if ammonia has spiked in the tank. Goldfish can still make a comeback, so keep your hopes high!

Remember, the black spots are the result of the restoration of the chemical burns. Monitor your fish’s conduct closely. If they are swimming typically and being perky, the goldfish ought to make a full recovery! In this case, the spots will progressively fade away. It takes time, but your goldfish will, in the end, return to its regular color. Just make sure that you take steps to tackle ammonia problems so that future burns don’t occur. And also, make sure that the aquarium’s health is maintained.

Other Methods to Prevent the Black Color.

  1. Test the water by using a testing kit and change the water
  2. Dose with Prime (to bind ammonia) 
  3. Add carbon to the water (as carbon binds toxins in the water)
  4. Limit food as reducing the food can help reduce ammonia.

A Goldfish’s Natural Habitat

The average lifespan of a pet goldfish is 5-10 years. However, their life can be prolonged by providing the best conditions and proper care to the fish. Aquarium health is one of the MAJOR factors to keep fish healthy and live long. Following are the further factors to keep the goldfish  healthy, perky, and vibrant:

  • Cool water. Goldfishes like cold water.
  • Room to grow as they need a larger area to evolve.  You’ll learn why larger space is vital by going through this blog.
  • A good diet such as flake foods and supplements of freeze-dried foods and vegetable matters. 


Now you have the expertise to discern why your goldfish is turning black and if there’s anything you need to do differently. Seeing these gorgeous fish darken over time can be an unhappy sight. Take all the needed safety measures to keep your fish alive and healthy. If it’s genetic, learn to appreciate this exciting alternate in color. It’s all a part of being a Goldfish owner!