Can Fish See Red Light?

There are different types of light that you can use for your aquarium setup. There’s blue light, red light, white light. Some setups even use multi-colored lights.

Can fish see red light? Not exactly, but light, in general, simulates daytime and nighttime for your aquatic critters. Just like us, fishes also use light to distinguish between their day and night.

Fish aren’t like us, in a sense that different colors of the day affect us. The faint light of sunrise is perfect for mountain views, the orange sunset skies when watching the horizon over the sea, and the purple light of dusk that contrasts the city skylines.

Inside buildings, we use different lightings and colors to perfectly stimulate the ambiance we want as well. Warm colored lights give off a cozy feel which is suitable for bedrooms. White and blue lights are for areas where you need to focus or pay attention to detail such as kitchens, utility areas, study rooms, and even bathrooms.

In this article, we’ll talk about whether fish can see red light, what colors of lights are good for them, and how light affects them.

Source: Reddit r/PlantedTank

Can fish see red light?

Technically, yes. Fishes have sensors that make them aware of the light around them.

If you’re talking about whether they can differentiate between the different colors though, not really. They don’t really see blue light and red light in a different way. To them, light is light, whether that light is red, blue, or white.

What color light can fish not see?

The answer to this question is both everything and nothing.

As mentioned, fishes don’t really distinguish the different colors of light from one another. All they know is that there’s either light, or there isn’t.

However, there are some light colors that fish can see that humans can’t. For instance, fish can actually see ultraviolet light and infrared light. These lights are invisible to our naked eye.

What does red light do to fish?

Source: AliExpress

To the fishes themself, there is no notable consequence to having red light as opposed to the color lights in their tank.

Most people who prefer red light over other colors simply choose it because it’s a great color for spying on fish at night. It’s not as intrusive as white light, and it also enhances the colors of a planted tank.

Ocean parks actually use red lights for their aquariums containing deep-sea creatures. Because red light doesn’t penetrate water deeper than 15 – 20 feet, for deep-sea creatures, having the red lights is almost the same as not having any light at all.

As such, red lighting is the closest to pitch black that the ocean park designers can provide so that humans can still see the inside of the aquariums while still replicating the animals’ natural habitat as much as possible.

Do colored lights affect fish?

Colored lights affect fish the same way daylight affects them. It depends mainly on how bright or dark the light is.

For fishes, generally, they require around 12 hours of daylight. Any less and some species such as the goldfishes can lose their colors. Some lose their appetite.

On the other hand, if there is too much exposure to light, the fishes may find it uncomfortable. They may also not be able to sleep since they use the presence and absence of light as a marker for their sleeping patterns.

What color light is best for fish?

This actually depends on what kind of fish you are keeping. But as a general guide, this depends on how much light is in the room or area where your aquarium is.

If you’ve placed your aquarium in an area where it usually receives lots of light, regardless of whether it’s from the sunlight passing through the windows or from fluorescent lights in the ceiling for most of the day, then there’s technically no need to put additional lights on your tank since your fishes are already exposed to a lot of it.

If you still want one, however, then red light is good since it will not disturb their sleep, even if you turn it on at night.

Other types of light like blue light are great for ambient lighting. You can use the blue light to mimic the transition from daylight to nighttime as the blue light reflects in the water similarly to how moonlight reflects in the water. However, be aware that the length of time the blue light is on is also counted towards the 12 hours of daylight your fish requires.

However, if your aquarium’s only source of light is the light you’re going to put on it, then it is best to use a white light as this is the light color with brightness and intensity that best simulates daytime.

There are even options out there that combine these colors, like blue and white, and red and white.

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