Why Do Goldfish Change Color? (Science & Causes)

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If you own goldfish, chances are you have likely noticed that sometimes they change color. This can be caused by a variety of factors – diet, amount of light exposure, genetics, maturing and aging, water quality, or in some cases disease or illness. The majority of color changes occur during the first two years of a goldfish’s life. Most goldfish start off as brown or black due to possessing melanophores, or specialized cells that contain melanin (biological pigment), within the dermal layer of their scales. This darker coloring, it is theorized, helps young goldfish survive by being able to blend in when hiding and escape the attention of predators.

common goldfish orange
Most common goldfish species will take on their classic orange color as they mature.

As they mature, goldfish will generally change to their characteristic orange or yellow coloring within about a year. Goldfish in environments with less sunlight available may not be as brightly colored as those in well-lit ponds, and so you can expect natural variations in color attributable to environmental factors throughout a goldfish’s life as well.

In addition, goldfish also possess pigment cells known as chromatophores (melanophores are a sub-type of chromatophores) that react most strongly with water temperature, but also respond to water quality, sunlight, and even the quality of their food, diet, and nutrition!

As you can tell, there are many factors that can influence the color of goldfish throughout their life; but what are the most common colors and changes to expect? And what should you do if your goldfish has suddenly changed color? Read on below to find out more.

Will All Goldfish Change Color? (Comparing Different Scale Types)

Most domestic goldfish exhibit three main scale types: metallic, nacreous, and matt. The presence, absence, and/or abundance of these scale types and the density of pigment cells within them also determines if and how a goldfish’s scales will change color throughout its life.

Metallic scales are composed primarily of a crystalline pigment known as guanine that mirrors light, and contain a high abundance of xanthophores and erythrophores, the cells primarily responsible for bright coloration like reds (xanthophores), oranges and yellows (erythrophores). Metallic goldfish typically have fairly stable coloring, meaning that it likely won’t change much during their life. Below is a video showing a goldfish with a heavy metallic scale type:

Nacreous scales contain some guanine, and so goldfish with this scale type may appear moderately metallic while others may not at all or will instead have a sort of mother of pearl appearance (it just depends on the amount and density of guanine).

Some nacreous goldfish color types (midnight, calico and bluebelly) may have scales that appear translucent. Nacreous goldfish are typically black, red, or yellow or some form of mixture of these. The pigment cells in nacreous goldfish are usually found beneath the scales, and as such this goldfish type may appear a bit dull and less bright. Their color will not typically change much as they age, though it is not uncommon for black nacreous goldfish to acquire more black coloring as they age. Below is a video showing a goldfish breed with a heavy nacreous scale type:

Matt goldfish lack guanine as well as pigment cells, and as such are typically white, pink, light grey, or cream-colored due to their skin color showing through their translucent scales. As may be expected, matt goldfish do not change color as they don’t possess pigment cells.

Why Has My Goldfish Turned White? (Possible Causes)

1) Insufficient Lighting

why do goldfish change color insufficient light
Ponds or aquariums with insufficient lighting can cause Goldfish to lose pigment and dull in color.

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. Without light, goldfish adapt to stop wasting energy resources on color production and maintenance. This results in the goldfish becoming either white or black, depending upon its dominant genes.

2) Natural Genetics

As mentioned above, there are three main scale types in goldfish. How goldfish are bred heavily influences the scale type and coloration of their offspring both as fry and as adults. For example, if a matt goldfish is bred with a nacreous goldfish, there’s a fifty percent chance that the offspring will be matt and a fair likelihood of some of the offspring becoming more dull or pale as they mature, even if they started off with color. Some goldfish varieties, particularly if two different types are cross bred, 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.

3) Poor Water Quality

If you’ve noticed your goldfish rapidly turning white, you should use a kit to test your water quality. Poor water quality (too much ammonia, too many nitrites, too little oxygen, high water temperature, etc.) can really mess with 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.

4) Disease or Parasites

white spot disease can cause goldfish to lose or change color
White spot, or Ich, is a common fish disease in both koi and goldfish.

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.

However, don’t think the worst if you notice your fish is turning white! The first step is to test the water quality and temperature of your tank or pond – if the pH, temperature, and nutrient levels are within the acceptable range for goldfish, it’s likely that the color change is natural and nothing to be concerned about. If you know where your fish came from, you can inquire about its lineage to determine if genetics is playing an obvious role in color change.

5) Poor Diet & Nutrition

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 color, such as carrots, peas, spinach, and spirulina, which can be found in many high quality pellet feeds. While a diet with carotenoid deficiencies likely won’t cause your fish to turn entirely white, you may notice your goldfish’s colors becoming a bit dull or pale.

Why Has My Goldfish Turned Black? (Possible Causes)

1) Natural Ageing

As mentioned previously, many goldfish start off dark brown or black and then gain more characteristic coloring as they mature. However, if your goldfish is over a year old and still black, chances are that you simply have a black goldfish! If it started off colorful or lightly colored and is now turning black, a few other factors could be involved, such as those explored below.

2) Poor Water Quality

goldfish can lose color due to poor water quality
Both water quality and pond maintenance play an important role in fish health, so should be kept to high standards.

Just as poor water quality can result in goldfish becoming pale, it can also cause them to darken as too many or too few nutrients, too many pollutants, and so on interferes with the goldfish’s ability to regulate its pigmentation. Utilize a water test kit immediately to assess the condition of your water. One of the biggest things you’ll want to check for is ammonia, which is produced naturally via decomposing food matter and fish excrement. Goldfish are heavy producers of ammonia, and if this isn’t filtered out properly your fish can develop black ammonia burns. The tricky thing about ammonia burns is that if the ammonia levels are consistently high, the skin will not be able to heal from the burns and so they won’t show up. The burns turn black once the ammonia levels have dropped enough for the skin to begin healing, so your best bet is to keep a close eye on your water quality and treat it and/or change the water if needed.

3) Disease or Parasites

Similar to white spot disease, black spot disease (or diplopstomiasis) causes black spots to form on goldfish. This particular disease is passed by a parasitic larval flatworm that inhabits aquatic snails. As the flatworms mature into adults, they exit the snail and burrow into the skin of any nearby fish. The fish respond by encasing the parasite in a black cyst. While this disease is not considered fatal to fish, you should still take care to remove any snails and infected fish from your pond if you find your goldfish are suddenly developing small black cysts, particularly if your goldfish variety is not known for acquiring black pigmentation.

4) Natural Genetics

Just as genetics may cause goldfish to turn white, they may also cause them to turn (or remain) 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.

What Can I Do About My Goldfish Changing Color?

Much of the time, color changes are determined primarily by genetics and there is little that can be done as it’s a natural process!

However, unless your goldfish is black you can somewhat influence its color by, as discussed above, providing a carotenoid-rich diet, such as with a high quality color enhancing food. Also, keep up on pond maintenance to achieve and sustain suitable water quality, regularly testing the water. Ideally, water should be tested once per week at the same time for each test. If the water quality is poor, be sure to test it daily (again, at the same time each day) as you work to improve it.

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