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Why Does a Goldfish Turn Black

why does a goldfish turn black

The goldfish is one of the easiest pets to take care of in the aquarium. Apart from being readily available, they have the ability to adapt well to the new environment. But this fish also takes pride in its shimmering gold color that brings an excellent view to your fish tank.

But what if the golden color suddenly turns black? It can be a worrying sight, but why does a goldfish turn black? This article will tackle this very rare situation as we deal with different causes that make the goldfish turn black in your aquarium.


Common Causes of Goldfish Turning Black

Sometimes, the goldfish in your fish tank turns black, and it is normal for you to wonder why it happens. There are different causes that make the goldfish turns black or change to other colors. Some of these causes may sound not alarming, while others show that your pet is in danger.

When you are overpopulating your aquarium with goldfish, it is normal to see the fish change its golden color to black. But why does it happen? This color change can have different causes or reasons, which are found below:

Natural Cause

In general, the goldfish species comes in various colors, including orange, red, yellow, white, silver, brown, and black. But what usually happens when a goldfish suddenly starts getting black?

The scales of a goldfish can possibly turn black because of some natural but harmless causes. I used to ask myself, why does my goldfish have blackspots? The answer is a natural cause which is coming from the melanophores, a type of skin cells of fish that comes with melanin.

If an aquarium is situated in a dark place or comes with a dark and rocky bottom, these cells produce more melanin, and the goldfish will begin to have black spots on the body and the fins. This color change in your goldfish is not scary at all because it is natural.

High-Level of Ammonia

In other situations, goldfish turns black because of non-physiological reasons, which can be a sign of danger to your fish. When you see a goldfish starts to develop black spots located on the fins or the body, it is probably because the water contains a high ammonia level.

When you are taking care of different species of fish, it can also mean a constant battle of preventing ammonia buildup in the fish tank. Ammonia is a toxic chemical that comes with a negative impact on fish in general.

The ammonia content of the water will increase when food residues and fish waste are stuck in the water of your fish tank. This case is called ammonia burns, where there will be black or brown spots that will appear when the fish’s skin begins healing.

However, if the ammonia level of the water is exceptionally high, then you will not see any visible symptoms. The skin of the fish will have no way of healing.

common causes of goldfish turning black

Blackhead Disease

There is also a pathology called blackhead disease which can cause the goldfish to change its color to black. This situation is not very common to happen in most aquariums but usually happens to fish living in outdoor lakes and ponds.

The primary reason for this disease to happen is when the goldfish will be transmitted and infected because of bird feces. Sometimes, it contains a parasite that is not good and brings danger to fish skin.

Although it’s very rare, this disease can be transmitted by snails that are living in your aquarium. For you to remove it, you will need to remove all the snails in your fish tank while also eliminating the parasites as well.

To prevent the goldfish from turning black, make sure to keep the fish tank clean always. You can also maintain the temperature at the desired level. If the goldfish has blackhead disease, they will develop real spots in the different parts of the body.

There will be some mild cases where you will see a couple of spots in the body. But in severe blackhead disease, they can potentially cover the fish’s whole body completely in black. If you ask if they can get to their original color, they may or may not retain their natural color.

Can the Goldfish Go Back to Their Original Color

A goldfish that has turned black may or may not get its original color back. It will all depend on the cause of the color change and the prognosis.

If the cause of the change is purely genetics, the fish will be forever like that for the rest of its life. It may not be what you have expected, but this situation will not affect the goldfish’s health and quality of life in any way.

If the reason for the goldfish turning black is because of the high level of ammonia in water, the prognosis is not good. This situation can be fatal in many instances, but do not yet assume that your goldfish will die.

Always remember that black spots are the results of chemical burns. What you do is monitor the behavior of the goldfish closely and see what happens. If the fish swims normally and moves very alive, the goldfish may make a full recovery.


There are many reasons why does a goldfish turn black. It can be annoying and sometimes hurting if you see your goldfish darken over time. The cause can be natural, which is okay, but if it is not a natural cause, you will need to do a lot of maintenance stuff in your aquarium. Meanwhile, learn how to appreciate the beauty of the goldfish while they are healthy.

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