Why do goldfish lose their color?

Goldfish were found to be losing their color when put in water that is moving. However, it has been found that goldfish lose their color gradually when they become old and big. Goldfish are known to develop patches of various colors. The color change is influenced by its diet. The diet that consists of carotenoids will cause the appearance of red and gold colors. The diet which includes some other precursors of pigment will display the black and blue colors. The pale and faded colors for the goldfish are due to illness. The development of color on the goldfish is also found to be influenced by light. The color patterns are not observed to have developed when the goldfish are placed in complete darkness for a long time. The fish appears dark colored when the background color is dark while the fish appears  light in color when the background color is light.

The fish’s colors are attributed to the presence of pigment cells known as chromatophores. These are again of two kinds. Light-absorbing chromatophores are xanthophores, cyanophores, melanophores, and erythrophores. The light-reflecting chromatophores are known as iridophores and leucophores. The organelles present inside the chromatophores are called as chromatosomes. These kinds of chromatosomes will establish the pigment cell color. For instance, melanophores consist of melanosomes which comprise the melanin pigment.

The color change in fish is two kinds called physiological and morphological. Physiological changes in color involve the distribution of chromatosomes in the pigment cells. If the chromatosomes are spread all over the cell, the color will be specific. If they are accumulated at one center point or corner, the color is not visible. In the case of morphological change, the chromatophores numbers will determine the color change. For instance, a tank that is painted inside with a dark color having a dark background, the fish growing in that tank will be dark. Either the melanosomes will get spread all over the pigment cell or the melanophores will divide and multiply more. So the former process is physiological while the latter is called morphological.

The loss of color by the goldfish as they grow is due to the phenomenon called as apoptosis. Apoptosis is cell death. Apart from this phenomenon, the loss of color is due to the suppression of the birth of new melanophores. The degree of color change is based on the genetic makeup of the individual fish.