Why Is My Goldfish Turning Black?

Why Is My Goldfish Turning Black? Your goldfish may start to acquire black spots for some reasons, including a change in the conditions of their tank or any one of some other potential causes.

Why Is My Goldfish Turning Black?

What is Goldfish?

The goldfish (Carassius auratus) is a freshwater fish of the family Cyprinidae of the order Cypriniformes. It is often maintained as a pet in indoor aquariums and is one of the most popular aquarium fish.

Goldfish introduced into the wild have become an invasive problem in regions of North America. The goldfish is a miniature member of the carp family, which also includes the Prussian and crucian carp.

It was initially deliberately bred for color in imperial China more than 1,000 years ago, and numerous unique varieties have since been established. Goldfish breeds vary widely in size, body form, fin structure, and coloring, having different combinations of white, yellow, orange, red, brown, and black are known.

Causes of Goldfish to Get Black Spots

A parasite condition can cause a goldfish in a pond or fish tank to acquire black patches on its skin. Parasites that are darkly colored burrow into the fish’s skin, resulting in itchy, raised black lesions. Goldfish can become black for a variety of reasons.

1. Inheritance of a Predisposition

Colorful goldfish are available. During China’s Song Dynasty, silver carp was changed to gold. Only royalty could have golden goldfish during the Song Dynasty; everyone else had orange ones. Goldfish are named for their color. They’re orange, white, yellow, and blue-gray. Goldfish are multicolored, like calico cats.

Your goldfish may be naturally black. Later, their color will become more dazzling and dark. This happens as goldfish develop. Color-enhancing goldfish food can make some fish more vibrant. If your goldfish isn’t a black-variant kind, black dots are unusual. Orange goldfish shouldn’t become black.

2. Ammonia Levels

Goldfish with no black variation in their coloration might have aberrant black patches appear. Your goldfish may suffer chemical burns if ammonia levels in your aquarium are too high. Your goldfish’s skin will darken as it recovers from the chemical burns, so once the ammonia levels return to normal, you’ll see black patches appear.

Check the chemical levels in your aquarium to be sure. It is possible to utilize a straightforward test kit or a more complex one. Goldfish are more tolerant of chemical changes than other varieties of fish, making them a good choice for aquariums with fluctuating pH levels. Although they need their water as balanced as possible, they nevertheless require it.

3. Black Spot Disease

Goldfish with Black Spot Disease have black patches. Parasitic Black Spot Disease can spread from snails to captive goldfish. Wild goldfish can get Black Spot Disease from snails or bird droppings. When a parasite enters a goldfish’s skin, cysts grow, according to the Indiana DNR. Cysts and scales make the goldfish black.

Black spot illness can form on fins, although body patches are easier to see. If your goldfish has a snail as a tank mate, visit a veterinarian about Black Spot Disease to keep your tank safe. Your goldfish may need to recover without snails. Black Spot Disease isn’t as deadly as ammonia poisoning to goldfish.

4. Illumination

Goldfish color changes are influenced by their surroundings. Goldfish may become black in a dark aquarium. Scale cells generate darker pigments in low-light conditions. Goldfish lose their color and turn white when exposed to low levels of light. This won’t hurt your goldfish, but if you don’t want one that’s black, you might want to avoid doing it. Add aquarium lights or brighten the environment to remedy the situation.

5. Overfeeding

If your goldfish is going black, it’s possible that overfeeding is a contributing issue. It’s a waste of time and money to give your goldfish too much food. The greater the ammonia levels in your goldfish’s tank, the more waste is generated.

Overfeeding a goldfish, who is already known to be a messy fish, can result in a filthy aquarium. It’s important not to overfeed your goldfish and to have a properly functioning filtration system in place to keep them safe from ammonia irritation.

Filtration can be accomplished chemically, biologically, or mechanically, depending on the type of media used. Veterinarians may be a great source of information when it comes to choosing an aquarium filter. They may prefer one method or need a combination.

6. Anxiety

Black spots on your goldfish may emerge as a result of their stress in the aquarium. Stress can cause your goldfish to become black, such as being bullied by other fish, being tossed around by the filter flow, or having insufficient water temperature.

Your goldfish may have injuries from fighting with other tank mates that show as black marks on their bodies. You may need to remove any fish from the group that behaving aggressively or is bullying the other members of the community.

The goldfish’s playfulness and curiosity may necessitate some changes to aquarium décor to accommodate the fish’s needs. Your goldfish may get damaged when swimming and feeding against any decorations that have sharp or rough edges.

Note: Keep an eye on your goldfish tank’s chemical levels, water temperature, fish temperament, and any other changes that may be taking place to keep them healthy and safe.

Why Did My Black Goldfish Stop Swimming?

Isolating your goldfish from the others is a smart idea if it isn’t swimming. Don’t try to relocate your fish out of their aquarium if they are still healthy and swimming about. Because of the potential of infection, relocating an injured fish is not a good idea. It has the potential to make your fish even more ill.

There are several things you may do to try to halt or slow down the pace of this color shift. If you’re suffering from anemia, for example, you’ll notice your skin turning black as a side effect. As a result, addressing their anemia may speed up the process of returning them to their original hues.

How to Prevent Goldfish from Turning Black?

Treatment or prevention of black spots in goldfish depends on the causes.

1. Cycle Fresh Tanks

Cycling your new tank requires adding microorganisms that convert ammonia into nitrate. Three ways exist. First, you may utilize robust fish like guppies and minnow to create enough ammonia, which will lead to more ammonia-degrading bacteria in your tank.

2. Upgrade a Small Tank

If you have five goldfish, it is probably a good idea to have a larger tank, such as a tank with a capacity of fifty gallons, because this will allow your fish to swim more freely and will minimize the accumulation of hazardous waste that is created by these goldfish.

3. Lighten Up Dark Ornaments

A lighter rock or ornament won’t make goldfish produce more melanin. If you suspect excessive ammonia levels in your tank, be sure you’re not overfeeding your fish. You’d also need a test kit to monitor ammonia, nitrite, and nitrate daily. Ideal tank ammonia levels are 0 ppm to prevent ammonia burns that create black patches on goldfish.

4. Remove Fish Snails from Aquarium

They might be a host for the parasite that is harming your goldfish, which would explain their symptoms. Tweezers are another tool you may use to remove parasites from your goldfish in a meticulous manner.

5. Remove Sharp Tank Ornaments

Since you are aware that sharp things pose a risk to the health of your goldfish, it is in your best interest to ensure that their tank is devoid of anything that might endanger them.

6. Replace a Broken Tank Filter

In addition to cycling, a high-quality water filter is essential for ensuring that your goldfish are provided with the ideal living conditions in which they may grow.

7. Change Tank’s Water Every 2 Weeks

Regular water changes remove debris, organic waste, and uneaten items that might build and create ammonia to injure your goldfish and cause black spots. To prevent black spots, which may be produced by adverse tank conditions, maintain good water quality by monitoring temperature, ph, and ammonia levels regularly.

8. Seek Medical Help

If you have tried all of these things, and your fish is still exhibiting symptoms, it is highly recommended that you take your goldfish to a goldfish expert or a veterinarian.


Some approaches kills fish, thus not recommended. Adding synthetic ammonia to your tank promotes the development of these bacteria and is faster. The final option includes adding ornaments or pebbles from another aquarium to your fish tank.

Frequently Asked Question - FAQs

Some related questions are given below:

1 - What should you do if your goldfish starts to turn black?

If you notice black spots on your goldfish, the first thing you should do is check your tank’s ammonia level with an accurate test kit. Overfeeding, decomposing organic materials in the tank, such as end plants and animals, and poor filtering can raise ammonia levels.

2 - Is my goldfish’s black going to fade away?

If the tank conditions or goldfish handling do not improve, the black spots caused by damage will recur. However, unless treated, a diseased fish retains its spots. A goldfish’s color may alter for good or for ill.

3 - Do ill goldfish have black spots on their bodies?

Eventually, the color of your goldfish will change. This may be a natural reaction. More than likely, your goldfish’s blackening is the result of a disease, rather than stress.

4 - Why are they referred to as “goldfish”?

A genetic mutation caused yellow-orange scales when breeding began. Anyone may wear yellow, the imperial hue, except royals. The people are called orange-colored goldfish.

5 - When your fish develops black spots, what does it mean?

One of the parasites that cause black spot disease is widespread in surgeonfish, but it may also infect other fish and mollusks (shellfish). A distinct type of parasite is responsible for ich, which is another name for black spot illness.

6 - Are goldfish man-made?

Goldfish aren’t native to the wild. The reason for this is that they were domesticated in China thousands of years ago and bred to produce the approximately 250 varieties seen in aquariums today.

7 - How can I tell if my fish is poisoned?

Unfortunately, it may be too late to save fish from ammonia stress if they show indications of lethargy, appetite loss, gasping, or inflammation of the gills, eyes, or fins.

8 - How long do goldfish live in a fishbowl?

One year is a long time for a Goldfish in a dish. A bowl’s typical lifespan is just two to three years if you do everything perfectly and replace the water often.

9 - Can my goldfish survive ammonia poisoning?

In fish, even very tiny amounts of ammonia can harm their gills, and even higher concentrations are generally lethal. If you identify this condition early enough and fix the water promptly, the fish will be able to live normally again.

10 - Does ammonia poisoning in a fish result in recovery?

If the damage is not too significant, the fish may be able to recover when the ammonia is removed. Ammonia typically damages the fish’s gills, thus increasing aeration could be a good idea. This has the potential to improve the chances of surviving just a little bit.

11 - Can goldfish survive in tap water?

Only water that has been treated to eliminate potentially hazardous pollutants can support the life of goldfish. If you use water from the tap, the “good bacteria” in your tank will be killed off.

12 - Can I put table salt in the tank for my fish?

Chemicals like iodine and anti-caking compounds, some of which contain tiny quantities of toxins like cyanide, are frequently used to treat table salt. Never use table salt in place of aquarium salt since it might be extremely hazardous to your fish.

13 - What foods reduce ammonia?

Ammonia may be digested and eliminated more successfully if you have these bacteria in your stomach. Fermented dairy products, such as kefir, and fermented vegetables, such as sauerkraut, are frequent sources of probiotics. Consume yogurt, for example, daily.

14 - What can I do to preserve my goldfish’s life?

Cool water from the goldfish’s tank should be used to keep the fish comfortable. Oxygen-rich chilly water will help recover your fish. If your goldfish seems dry, some experts recommend putting him back in the tank and giving him a good soak.

15 - How do you remove ammonia from water naturally?

Boiling water can lower free ammonia levels, but it has no impact on ionized or dissolved forms of the nitrogen gas. Ammonia reduction may be aided by some reverse osmosis, ion exchange, or distillation systems.


Some fish have black patches, so you should still inspect them. Fin clamping, air gulping, and ragged or shredded fins indicate water or tank problems. Always check water parameters. Poor water quality is the leading cause of sickness in goldfish, including infections, parasites, burns, and fin damage. Even if you think there’s no problem, check your goldfish’s water. Better safe than sorry with water quality and goldfish black patches.

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