Home Fish Science Can Fish See Red Light? (Complete Explanation)

Can Fish See Red Light? (Complete Explanation)

by gvald

Light allows to delimit a life cycle between activity and rest. Lighting is essential for fish, and for plants that need it to perform their photosynthesis. There are many types of lamps to light your aquarium, but for goldfish a simple light is sufficient.


However, most aquarium owners have asked themselves at least once in their lives, what color light to use for their aquarium? We will try to answer this question:


What color to use for the light of his fish?

The color of light is established in Kelvin units. The lower the Kelvin number of a light, the warmer and more golden the light will be. Conversely, the higher the Kelvin number, the more “pure” the lighting will be, comparable to daylight.


For classic aquariums with fresh water, the recommended light color is daylight, i.e. the equivalent of lighting between 6500K and 8000K.


On most lighting, you will find the characteristic “CRI”, which corresponds to the color rendering index and which is between 0 and 100 Ra. More clearly, this index corresponds to the quality of the lighting, if it is able to reproduce accurately the original colors of the objects it illuminates. The lighting will be of better quality when the index is closer to 100 Ra.


Do fish perceive red light?

Most of the time we use blue light, which doesn’t seem to bother the fish too much, but what about red light? Long story short, no, fish don’t differentiate between red and other colors.


This is not necessarily a good idea. Even though it has been proven many times that fish could not detect red light, it is however the color that seems to be the most absorbed by water. In this way, red does not really penetrate beyond the first 15-20 feet of the water column.


As far as sleeping is concerned, there is no concern, since the fish will not know the difference between red and any other color.


Can my fish have too much red light?

Yes, too much red light, or even any other color, can be as bad as none at all. It is therefore recommended leaving the aquarium lights on for a maximum of 8-12 hours per day and to have a light level that is appropriate for your tank (too much light can also promote algae and stress the fish).


Why is red light so different from the others (for us)?

Red is the color at the end of the visible light spectrum, next to orange and the opposite violet. It has a dominant wavelength of about 625-740 nanometers. Reds range from brilliant scarlet and yellow-tinged vermilion to bluish-red purple, and vary from pale red-pink to dark red-burgundy.


Since red is the color of blood, it has always been associated with sacrifice, danger and courage. Modern surveys in Europe and the United States show that red is also the color most commonly associated with warmth, activity, passion, sexuality, anger, love and joy.


In China, India and many other Asian countries, it is the color symbolizing happiness and good fortune.

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