Why Do Goldfish Change Color? A Colour Decoder for Fish Keepers

Did you know this: a goldfish can get a kind of suntan, a little like a human does. It can darken in strong natural light and can turn paler when kept in low light for an extended period of time. If your orange fish has now turned white, or your bronze baby is now gold, it's not your imagination. Why do goldfish change color, and should you be concerned? Decode it, colour by colour!

Match what you see with the most probable cause from this table. Next, read the deep dive below for each.

A large percentage of goldfish are born a dull bronze or brown color. They mature to orange, red or white as they grow. A fish veterinarian explains this in a famous video about goldfish colour. Some fish come to a halt halfway and continue to maintain their in-between shade throughout life. This tendency is most likely to occur during the younger life stage but can occur at any life stage.

If your fish was not the same when you got it home, the first thing to consider is growing up.

The special skin cells, called chromatophores, are responsible for the goldfish colour. UC Santa Barbara's ScienceLine explains that these cells make yellow and red pigments. Sunlight, with its UV rays, stimulates these cells to produce more pigment. In fact, pigment can even provide protection against high light intensity to the fish.

Most tank lights do not give the same full light as the sun, so over time a fish kept only under them can look paler. In some fish, such changes can occur in less than 30 days, ScienceLine says. Your fish might also appear somewhat washed out when the tank lights first come on, but appear brighter later in the day.

Many are surprised to hear this. Research shared by the University of Florida says that some red, orange and yellow pigments are not produced naturally by fish. These need to be obtained from their diet in the form of natural pigments, known as carotenoids. Colours gradually fade if these pigments are missing from the diet. That's why fish raised outside in ponds often have a brighter look. Colour is maintained with a balanced, good quality diet.

In goldfish, black colour is due to a cell type called melanophore. In normal colour change, the dark shade spreads evenly, often reaching the tips of the fins, back or around the mouth, similar to a small moustache.

However, if the black patches are irregular, lumpy or random, then it is another matter. This usually follows damage to the skin, such as an injury or an attack by a cat or bird, the fish vet in that video explains. Poor water quality and parasites should be ruled out first. If it is a patchy and not symmetrical pattern, to be safe, get your fish checked.

Generally ill fish do not turn a different colour, says Vet Dr Erik Johnson. Rather, they are faded, darker or dull. Look out for these signs along with the colour change:

If any of these are observed, test your water first. The ammonia and nitrite issues are common in small tanks. We've listed many common habits that cause fish stress in our guide to common goldfish care mistakes.

Setting up a tank? Our fish tank setup guide for India is a good place to start.

Therefore, why do goldfish change color? Age and light and diet – mostly due to these factors which are natural and harmless. Even, slow changes are generally not a problem. Sudden fading, dull skin or patchy black marks are the ones to watch. Use other signs of behaviour as well, such as fish swimming upside down, in conjunction with colour checks, and you will be catching problems early.