Our pets are precious to us, no matter whether they have scales or fur. Else we wouldn’t be pet owners. Your little goldfish is just as important as any other pet, so when you notice your goldfish changing color, you get concerned. 

You’re probably asking, “my goldfish is turning black what should I do?” Should you be worried? Should you go to the vet? Is your little goldie going to make it?

Let’s take a look at some of the primary causes this may be happening and what you should do about it, if anything.

two goldfish turning black

Why Do Goldfish Turn Black?

There are multiple reasons that could be the cause of your goldfish turning black. Some are scarier than others, certainly, but many are natural and don’t mean anything in regards to your goldfish’s health.

Your Goldfish is Blending Into Its Environment

First off, all fish have different cells in their skin. Some of cells produce a black pigment called melanin, which naturally could be the cause of your goldfish tail turning black. It could also be the cause for scales turning black.

If you have your goldfish in an aquarium that has a dark backdrop – such as dark wall paper or a dark 3D background – your goldfish could start producing more melanin than normal. The reason? Your goldfish is naturally blending into its background. This is a safety thing built in for the protection of fish that are otherwise easy prey for certain larger fish.

This coloring could be across the whole body or it could be in patches along the scales, tail, or fins. This kind of color change is totally natural and absolutely nothing to worry about.

Your Goldfish Has the Genetics For It

There are many goldfish species that are blended breeds – meaning they have not been carefully bred to maintain specific qualities, such as coloration. This means these “mixed” species aren’t guaranteed to keep a specific coloring, including orange instead of turning black.

Most of these color changes due to genetics will happen in the goldfish’s first year of life, but not all. You might also notice the changes gradually happening at the fish matures. Often, lighter areas will appear along side these darker areas when this happens due to age.

So, in this case, what does it mean when a goldfish turns black? Simple genetics.

goldfish turning black in aquarium

Your Goldfish Could Be Suffering from Ammonia Poisoning

One of the most dangerous causes of goldfish scales turning black or goldfish fins turning black is that your fish are suffering from ammonia poisoning.

Goldfish are notoriously messy fish. They’re also regularly overfed by folks who consider them a casual pet. But when their messes aren’t cleaned up and their extra food is removed from the aquarium, the waste rots and released toxic ammonia into the water.

This causes many severe health issues that ultimately end in death for your fish. So check your water parameters often to make sure this doesn’t happen.

If ammonia levels are high enough for your goldfish to turn black, then your fish has actually had small burns on his scales and skin. Once you remove the waste – and give a water change of 60% – the ammonia levels should begin to drop. The damaged skin and fins will start to heal. Black patches will start to show up at this point. They will probably remain forever, unfortunately, because the skin, scales, tail, fins, et cetera have been severely damaged.

Contracting Black Spot Disease

The next concern folks have, asking, what happens when a goldfish turns black, is the possibility of black spot disease. Thankfully, despite the popularity of this theory, black spot disease is actually pretty rare, especially in adult fish.

Black spot disease will only be the cause of your goldfish turning black if you keep snails in the same tank with them. It’s more likely to happen in an outdoor pond, as well, rather than in an aquarium. This is because of snails but also because of bird droppings landing in the pond.

Black spots come from a parasite, not an infection. The parasites lay eggs, which turn into larvae, which then burrow into the skin of the fish. The fish will start to form hard cysts to protect themselves, and these cysts are very dark or black, which is where the name comes from.

If there are dark spots like this, your fish will also likely start flicking its tail and rubbing against surfaces because of being irritated.

If you have snails and your fish seems to have developed these cysts and is showing these other signs, you should remove the snails immediately.

Overfeeding Issues

So, why do goldfish turn black? Another reason can be overfeeding. Goldfish are particularly prone to this problem, especially when they’re new to their environment. Overfeeding not only creates waste in the aquarium, but it can cause issues for the filter working properly. This in turns causes other problems. Ultimately, this results in your fish discoloring, becoming ill, and potentially dying of swimbladder disorder, ammonia poisoning, or something equally painful.

To alter this issue, keep better track of feeding. Read up on the subject, keep notes on how much your fish eats, and remove food waste immediately.

orange and white goldfish turning black

Stress and Other Illnesses

Finally, another reason for your goldfish turning black is that he is ill or stressed. We’ve already talked about black spot disease, which is extremely rare and ammonia poisoning, which is far more common. There are other illnesses and diseases that may also cause these issues.

Sudden changes in the environment, introduction of other fish or animals may also cause discoloration, a well, because of the stress. This is especially likely to happen to a fish that has recently been shipped, moved, or had other environmental changes.

If the stress is the cause, generally a little time will help your goldie recover. If, however, illness is the problem, you’ll need to consult your veterinarian to get some help.

Will Your Goldfish Be Black Forever?

Not only have you been wondering why is my orange goldfish turning black, but you’ve probably also wondered if your goldfish will be black forever.

Some of the situations, a goldfish will return to his normal coloring. Other times, he won’t.

If your fish is changing color due to the environment, remove dark elements such as a background, and he will likely return to that same vibrant orange.

Genetics, most illnesses, and ammonia poisoning will result in permanent color changes.

Overfeeding and stress may go either way.

How to Prevent Your Goldfish from Turning Black in the Future

orange goldfish with black spots in pond

So, now that we’ve answered, “Why is my goldfish turning black?” let’s take a look at ways to prevent it from happening again in the future for other goldfish.

  1. Regularly check the ammonia levels in your aquarium.
  2. Avoid overfeeding. Remove waste food immediately.
  3. Clean the aquarium regularly.
  4. Avoid housing snails with goldfish.
  5. Use bright or light-colored background and decorations – avoid using dark elements in the aquarium.

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