How the colors are created
The colors of the fish come about in three different ways:
- by chemical staining
- by physical coloring
- by direct pigment coloring, which is actually also a chemical coloring
Chemical coloring
The chemical coloring is mainly produced by guanine crystals. Fish store guanine crystals in their epidermis cells, ie the skin. These crystals reflect the light brightly or whitish. White fish are a case in point. At the same time, guanaine crystals are a kind of excretion product of the nitrogen metabolism.
Physical coloring
Depending on the incidence of light, the light is refracted on the scales and the embedded crystals. This mainly creates bluish tones. Congo Tetras are a good example.
The chemical and physical coloring cannot be actively controlled by the fish.
Direct pigment coloring
Direct pigments are primarily melanophores, black color cells, and carotenoids, red-yellow color pigments. With the direct pigments, fish can actively influence their body color. Both are more or less indirectly under hormonal/nervous control and the expansion of the pigments in the skin can therefore be controlled.
The 3 types of color explain why fish, for example, often simply turn pale at night. The guanine crystals are clearly noticeable at night and the fish look whitish, just pale.
Many species of fish also change color when they are stressed. Many fish feel more comfortable in an aquarium with lots of plants, a safe and calm environment, dark substrate, etc. and then show particularly beautiful colors.
If fish in the retail tank are pale or stress colored, it may make sense to view the desired fish for several days in a row. Fish usually get used to it in a few days and lose their stress colors.
Some fish are said to be «polished» with hormone supplements when farmed or even traded. When such fish come out of these hormone baths, they become paler and return to their natural colors.
The red parts of the coloring can be refreshed with noble sweet rose paprika or carotene, which is mixed with the feed.
Why are many fish brightly colored?
© mikhailg – Fotolia.com
Because it is relatively dark under water, the question arises as to why many fish species are brightly colored. Everything looks more or less gray in the dark. Also, bright colors in nature are usually warning colors. Many colorful fish species, such as red neon, are not exactly dangerous.
Bright red is the first color to disappear under water and fish are gray, dark gray or even black among their peers. The gray value of their coloring actually serves them as camouflage.
These fish aren’t just gray because the fish probably don’t care. They simply use an available pigment in their body to color themselves. If it then looks gray to the other fish, then that’s fine. The fact that people perceive this color as bright red or bright orange is irrelevant in this context. We perceive the world with our sense organs and not the world as it actually is. This also applies to the fish. Perhaps red pigment is easier to produce than gray pigment for the appropriate fish species. Possibly it is energetically cheaper.
The conspicuous coloring is often there to dissolve the body outline and distract from the head, eg false eye spots. An example outside of the fish world is tigers, which are almost invisible in dry grass because of their stripes.
The coloring often also serves to identify oneself to other species and thus to mark out territories.
© Carmen Brehm Cockatoo dwarf cichlid
Frequently, the fish males also have to impress the females with the most conspicuous splendour. A well-known example outside of the fish world is the peacock.
In the case of schooling fish, such as neons, the coloring serves to shimmer in the closed school. This is a shoal behavior to irritate predatory fish. It makes it impossible to focus on a single animal. In the sea there are schooling fish called “fusiliers”. Some species look like oversized neons.
Incidentally, fish have a completely different world of perception than we do. Because of the lateral line organ, it is almost impossible for a fish to want to hide. Other fish notice him from afar at the slightest movement. And the eyes are different from humans, too. For example, goldfish can see both infrared and ultraviolet. They perceive two colors more than we humans.
However, this does not apply to all fish species. The ability to see must be proven separately for each fish species. For example, pike can only see colors to a limited extent, like cats and dogs. However, pike can see movements very well and night vision is also extremely pronounced.