Why Is My Goldfish Changing Color?

Did your fish turn lighter color?

Is your fish tank positioned in a partly shady place with no artificial lighting?

Is the aquarium water of poor quality?

Is the color change accompanied by lethargy, lack of appetite, growths on the scales/fins, or the development of white spots, etc?

Do you feed your fish a non-varied diet?

Did your fish turn darker color?

Is your goldfish getting black spots all over its body?

Perhaps the most common non-natural cause of goldfish turning white or becoming dull is insufficient lighting. For maximum color enhancement and to ensure that color develops properly as goldfish mature, 12 hours per day of either sunlight or artificial lighting should be available. Lack of light can, depending on the goldfish, promote the production of melanin (black pigment) or decrease chromatophore (the cells that produce color pigments such as yellow and red) production.

Poor water quality (too much ammonia, too many nitrates, too little oxygen, high water temperature, etc.) can disrupt your goldfish’s ability to regulate cell pigmentation. An excess of nutrients, in particular, is liable to cause any pigments that are present to concentrate, resulting in either pale or dark fish depending upon the goldfish variety and its genetics.

If your goldfish has become white or dull and this change is accompanied by symptoms such as lethargy, lack of appetite, growths on the scales/fins, or the development of white spots, your goldfish may have some form of disease or illness. White spot disease, or ich, will cause white spots to pepper the fish’s scales, and other symptoms include lethargy, difficulty breathing, and swimming, and even death. Typically, the disease is either passed on by other infected fish or is triggered by poor water quality.

Try to feed your goldfish a varied diet, as they can naturally lose a bit of their color when not obtaining the right nutrients. Carotenoids are fat-soluble red, yellow, or orange pigments responsible for giving goldfish their characteristic coloring. However, goldfish cannot produce these pigments on their own and as such should be fed supplemental foods that are rich in carotenoids that may help to naturally enhance colors, such as carrots, peas, spinach, and spirulina, which can be found in high-quality pellet feeds.

Some goldfish varieties, particularly if two different types are crossbred, may naturally undergo a process called demelanization as they age. This gene triggers the loss of melanin, and gives rise to any dark scales on the fish paling or turning entirely white.

Too many or too few nutrients or too many pollutants can interfere with the goldfish’s ability to regulate its pigmentation. Goldfish are heavy producers of ammonia, and if this isn’t filtered out properly your fish can develop black ammonia burns. If the ammonia levels are consistently high, the skin will not be able to heal from the burns. The burns turn black once the ammonia levels have dropped enough for the skin to begin healing.

Black spot disease (or diplopstomiasis) causes black spots to form on goldfish. It is passed by a parasitic larval flatworm that inhabits aquatic snails.

Genetics may cause goldfish to turn black. If you didn’t breed the goldfish yourself, see if you can find out its ancestry. If your water quality is healthy and you know that no diseases are present, your fish is almost certainly changing color naturally. Black pigmentation is not known to be influenced by diet.