Can Fish See Red Light? [What Light Can Fish See?]

Image of red light on water

Whether fish can see red light depends on where they live and under what conditions. Fish in shallow waters use cone cells to see the red light. But red light is the first to get absorbed by water. So most deep ocean fish can’t see the red light in their natural habitat as it fades and turns dark.

Let’s talk about this in more detail now.

What Light Can Fish See?

Fish are trichromatic and can see red, green, and blue lights. However, some fish can see a fourth color – ultraviolet light. Like most animals, fish use rod cells in low light or at night to detect contrast and movement. On the other hand, cone cells help them distinguish various colors.

Given below are the water conditions and depths at which fish see different lights.

1. Wild Habitat

Most fish have an excellent close-up vision but a poor distant vision. However, their visual acuity varies based on the habitat they dwell.

Therefore, a particular light looks different at the same depth in different conditions.

Clear Water

The Wisconsin Sea Grant study shows how five primary colors lose integrity with depth until they become grayish-black in clear water.

The color red, which has a short wavelength, turns dark at 30 feet and orange at 50 feet.

Yellow color is seen until 100 feet, while green is much longer, around 130 feet.

Finally, blue fades to black around 150 feet in scant daylight.

Turbid Water

In shallow but turbid water, colors appear different than they would if viewed from above.

In addition, the light fades more quickly in turbid water than in clear water, but the wavelengths of the lights don’t determine their visual integrity.

In turbid waters, blue color light is hard to see except at the surface.

Orange and red colors are seen around 6 feet. However, the colors green and yellow penetrate more than 10 feet.

Therefore, depending on the living habitat and conditions, fish are exposed to different lights.

Some fish live for years without ever seeing any color other than blue.

Other fish see colors like red, green, yellow, orange, purple, blue, etc.

They see differently depending upon where they live and under what conditions.

2. Aquarium Habitat

In captivity, fish live in a controlled environment.

The water temperature and quality are mostly stable and only experience slight variation.

In addition, unlike their natural habitat, aquariums are shallow and smaller in size with less debris or particles that scatter or absorb light.

So light penetration is more compared to the natural habitat of fish.

Therefore, fish living in an aquarium see the light more accurately as it doesn’t get absorbed quickly, and the tank size is small and shallow than their natural habitat.

Can Fish See Red Light At Night?

Fish can’t see the red light at night. Moreover, colors don’t matter to the fish in low light or at night. Fish rely more on rod cells than cone cells to detect both movement and contrast. Deep-sea fish live their entire life in darkness; they use their eyes for hunting but not for seeing.

Deepwater fish navigate using lateral lines, rows of pressure-sensitive organs that run down each side of their body.

It allows the fish to sense nearby predators or prey with the help of the pressure change or tiny vibrations in the water.

Can Betta Fish See Red Light?

Yes, betta fish see red light as they have good eyesight. However, they see clearly only for shorter distances. This is because they have more cone cells than rod cells in their retina, enabling them to perceive colors accurately when they focus on nearby objects.

Generally, betta fish see red, green, and blue in their natural environment and distinguish between them.

However, some betta species see colors better than others.

Certain betta species such as the Crown tail and Veil tail have good color vision, whereas others like the Comb tail, Delta, Double tail, and Half Moon have poor color vision.

As a result, they can’t distinguish between black and white colors.

The visual acuity of betta fish varies depending on their surroundings, so what light they see varies in different environments like lakes, rivers, and aquariums.

Can Saltwater Fish See Red Light?

Saltwater fish in deep oceans generally can’t see red light because it gets absorbed by seawater. However, fish living in shallow waters see red light before it fades away. Furthermore, if the water has already attenuated some colors, then those colors get muted or even appear grey or black.

Saltwater fish that live in inshore waters see more colors due to their proximity to land.

However, inshore waters usually contain more particles, and so light gets absorbed and scattered quickly. 

Fish living in inshore waters have more cone cells than rod cells. It allows them to distinguish colors accurately.

Offshore saltwater fish mostly live in deep waters.

Therefore, red, orange, and yellow lights with long wavelengths get absorbed quickly compared to lights with short wavelengths, like blue.

Since most colors don’t penetrate deep in water, rod cells are more useful for fish than cone cells.

Fish species living at great depths use rod cells to detect the slightest contrast between moving prey and the faint light coming from the surface.

Can Tropical Fish See Red Light?

Fish that live in tropical waters are called tropical fish and inhabit the warm waters near the equator.

Freshwater tropical fish live in freshwater lakes and rivers; tropical saltwater fish live in ocean waters.

Tropical fish living in shallow parts of the river and lake see red light. However, the water conditions determine how deep the light travels before turning black. Similarly, tropical saltwater fish near the shore see red and other colors more accurately than offshore fish living in deeper waters.


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