Why Is My Goldfish Turning Black? Learn What It Means & How to Cure It

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 turning black, 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.

Should I Be Concerned About My Goldfish Turning Black?

While most of us know that some goldfish are naturally black in color, are partially black (think calico and koi patterns) – an orange goldfish suddenly turning black in their freshwater aquarium can be quite concerning.

But is there ever a good, healthy reason for a goldfish turning black or should you always be concerned if this change occurs?

Goldfish turning white is a far more common occurrence, but goldfish may turn black for a variety of reasons that you definitely need to investigate.

This color change could mean anything from something completely natural and healthy to something as dangerous for your fish as internal injury.

Before you panic, read through the reasons and see if any of these things have occurred for your fish. Then, make a game plan (if needed) to help your little goldie.

Reasons Why Is Your Goldfish Turning 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 regarding your goldfish’s health.

Author note: Black is the least stable color for goldfish. They’re more likely to turn white or pale yellow than black. It is rare for a goldfish to turn black.

Because of this rare occurrence, most folks automatically conclude that there’s something terribly wrong with their fish.

This may be the case, but sometimes it’s simply a natural change that occurs due to environmental changes, maturing, or other natural causes. You don’t need to automatically assume your little guy is in trouble.

Instead, look through the list below of reasons for your goldfish turning black before taking any steps. You could help save your goldfish’s life or just make them more comfortable, depending.

1. Your Goldfish is Blending Into Its Environment

First off, all fish have different cells in their skin. Some 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.

Author Note: If you have your goldfish in an aquarium that has a dark backdrop – such as dark wallpaper 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 with the scales, tail, or fins. This kind of color change is totally natural and absolutely nothing to worry about.

This change especially may occur because of the lighting you’ve provided for your fish.

These melanin-producing cells respond to the lighting in which goldfish live. The darker the environment, the more likely your goldfish is to turn black.

2. 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. They may, as they mature, simply turn black because of these genetic markers in their DNA.

Most of these color changes due to genetics will happen in the goldfish’s first year of life, but not always. You might also notice the changes gradually happening as the fish matures in the next few years of their life.

Top Tip: Often, lighter areas will appear alongside these darker areas when this happens due to age.

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

It should also be noted that as goldfish become older, they may become white with age. If your older goldfish is starting to turn black, it is unlikely to be a natural change due to genetics. Your goldfish is surely dealing with something else.

3. 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. This is sometimes referred to as ammonia burns when it shows up in the coloring.

Goldfish are notoriously messy fish. They’re also regularly overfed by folks who consider them casual pets.

So, when their messes aren’t cleaned up and their extra food isn’t removed from the aquarium, the waste rots and releases toxic ammonia into the water.

This causes many severe health issues that ultimately end in death for your fish. If there is ammonia in the tank, black patches will start to show up at this point.

Other signs your goldfish may have ammonia poisoning are inflamed, reddened gills, any blood vessels showing through their skin – especially in fins and tails – and thick mucus patches on their sides.

If your goldfish has started turning black, the immediate course of action is to check your water parameters. Use a test kit to make sure you know exactly what you’re looking at and take action from the results.

Author Note: If ammonia levels are high enough for your goldfish to turn black, then your fish has actually had small burns on its 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. The coloration of your goldie may return to normal if you catch it early enough.

However, the black spots will probably remain forever, unfortunately, because the skin, scales, tail, fins, et cetera have been severely damaged.

4. Contracting Black Spot Disease

The next concern folks have 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.

Once you remove the snails, it will probably take about a month – up to two – for the cysts (and therefore the black spots) to go away.

If the problem persists, you may need to give your fish some anti-parasitic medications.

5. 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 to work properly. This in turn 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.

6. Other Illnesses

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 color change issues as well – and if your goldfish turning black seems to not reflect any of the other issues addressed, it is likely one of these other illnesses.

7. Your Fish is Stressed Out

7. Your Fish May Be Stressed Out

It might seem like fish shouldn’t have that much to get stressed out over – after all, they eat, sleep, and poop, and that’s pretty much it – but fish can be stressed out pretty easily.

This is especially likely to happen to a fish that has recently been shipped, moved, or had other environmental changes.

Stress in fish occurs for a variety of reasons including

• Being bullied – If any other fish in the tank is overly territorial and a given goldie is calmer, it will likely be bullied and therefore will get stressed out.
• A sudden change in environment – Whether your goldfish is new to your tank or the tank itself undergoes changes, this can stress out your fish and cause issues.
• New additions to the aquarium – New fish, decorations, or other additions can stress out your pal and start issues of goldfish turning black.
• Water parameters making it difficult to feel good – Yes, fish get stressed out by poor health and reactions to their environment, too. If your goldfish is turning black, it could well be due to water conditions stressing them out.

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. So, be sure to check parameters immediately before making decisions.

Author Note: Sudden changes in the environment, the introduction of other fish or animals may also cause discoloration, a well, because of the stress.

Learn More: Why is my goldfish turning white?

8. Your Fish Could Be Healing From Injuries

It’s also possible that your fish’s tone is darkening because of an injury sustained during a fight, by bumping into objects in the aquarium, or other ruckuses.

Just like the human body works, with doing things to attempt self-healing, goldfish also have this kind of mechanism.

For goldfish, healing tissue often looks black. There may be little patches of black popping up where the goldfish has bruised itself or injured scales or fins.

Watch the black spots on fins, tails, and sides carefully. If the patches lessen, the goldfish is probably fine.

If, however, the goldfish starts developing other symptoms, consult a vet on what can be done for the fish. The injuries could be more serious.

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.

In some of the situations, a goldfish will return to its 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

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.