Can Goldfish See In The Dark? (All You Need To Know)

Goldfish are the most common species that every beginner and veterinarian fish keeper prefers to add to their home aquarium. 

Your fish have superior eyesight better than humans, but can they see in the dark? Can your goldfish see in the dark? Do they need light? Let us find out.

Goldfish cannot see in the dark despite superior eyesight, and they rely upon their tremendous sense of smell during that period. In addition, the lateral line organ(LLO) in goldfish helps sense any movements and vibrations in the water, allowing them to locate their prey or predators in the dark.

The below article will discuss the need for light and dark periods for your goldfish. In addition, we will also discuss the cons of keeping your goldfish in complete darkness 24/7.

Can goldfish live in the dark 24/7?

You should not keep your goldfish in the dark 24/7 as it can lead to significant health issues for your goldfish.

If deprived of light, your goldfish will not be able to survive for an extended period, as it can make your fish lose their natural colors and suffer from excessive stress, leading to the passing away of your fish.

You should provide light to your goldfish for their proper growth and development in the daytime.

Likewise, human goldfish are also diurnal that rely upon a healthy alternation between daytime and nighttime.

Your goldfish should get a balance of light and dark periods in their tank for their well-being.

Lack of light in the tank can lead to stress in your goldfish, and your fish can also lose their color.

Excessive stress can also lead to severe health issues, eventually leading to the passing away of your fish.

Therefore, you should always provide light and dark periods in your goldfish tank for the well-being of your goldfish.

Also read: What To Do If My Goldfish Is Stressed?

How good is the eyesight of goldfish?

Goldfish have superior eyesight than humans, as we can see three colors with all their combinations( Red, Green, Blue) RGB.

But, on the other hand, goldfish can see those colors and the ultraviolet lights, which makes them sensitive to polarized light that allows your fish to locate their prey or predator through water surfaces and avoid troublesome reflections.

Goldfish can see up to 15 feet (4.5 meters), allowing them to see outside the tank and scan any sudden movements in the aquarium.

However, your goldfish cannot see in the dark as at that time, and your fish rely upon their tremendous sense of smell.

In addition, goldfish also have an incredible hearing sense that helps them detect any vibrations and movements in the water.

How does your goldfish navigate at night?

Your goldfish cannot see in the dark, so they navigate through their incredible sense of smell at night.

Your goldfish can uses their sense to navigate around the tank.

The inner ear, located inside your goldfish’s head, and the lateral line, which runs both sides of the body, help your goldfish detect the movements and vibrations inside the water, allowing them to locate any predators in the tank.

So, even if your goldfish cannot see in the dark, they can navigate and protect themselves with their tremendous sense of smell at night.

Also read: Can Goldfish Hear Sound?

Can your goldfish see outside the tank?

Goldfish can see outside the tank as it has superior eyesight and can see up to 15 feet. Your fish is sensitive to polarized lights, allowing them to recognize you when you come near the tank to feed them. Goldfish cannot see the activities beyond 15 feet as things get blurry after such distance.

As your goldfish are sensitive to polarized lights, they can gather near and recognize you when you come near the tank to feed them, even on a sunny day.

So, your goldfish can detect movement outside the tank due to superior eyesight.

Can goldfish eat in the dark?

Due to their tremendous sense of smell, your goldfish can locate the food in the tank even at nighttime.

However, goldfish are diurnal that rely upon the healthy alternation between daytime and nighttime, which means they prefer to eat in the morning and rest throughout the night.

However, your goldfish will only prefer to eat at night if they are hungry or deprived of light during the daytime.

Should goldfish have a light at night?

You should not have the aquarium lights on at nighttime as goldfish are diurnal and rely on healthy alternation between day and night.

You should provide a balance of the light period and dark period in the tank as lack of either period can make your goldfish unhealthy and stressed, eventually leading to the passing away of your goldfish.

You can turn on the aquarium lights for 12-13 hours a day and switch them off at night to maintain the day and night cycle.

It will be advisable to add a timer control to the aquarium lights to develop a healthy rhythm in which they eat during the daytime and sleep at night.

Do goldfish sleep at night?

Your goldfish prefer to sleep when it is dark and quiet. Your fish do not have eyelids, so they rely upon total darkness to sleep.

However, if you make noise near the aquarium while your fish sleep, they will startle awake.

Likewise, human goldfish have a diurnal behavior: they prefer to eat during the daytime and rest at night.

Therefore, it will be advisable not to make noise around your sleeping goldfish for their well-being.

Do goldfish need light in the day time?

Your goldfish require light in the daytime as complete darkness in the tank can lead to significant health issues like stress in your goldfish, eventually leading to the death of your fish.

You should provide a balance of the light and dark period in the tank for your goldfish’s proper growth and well-being.

Leaving the aquarium lights on for the whole day can also lead to the rapid development of algae in the tank, further contaminating the tank’s water.

You can add a timer to aquarium lights to create a healthy routine for your goldfish in which they eat during the daytime and rest throughout the night.

You can turn on the aquarium lights for 12-13 hours a day and switch them off at night to maintain the day and night cycle.

A good day and night cycle helps your goldfish’s eye development and offers them the light requirements they receive in their natural habitat.

We advise you to purchase Hygger Spectrum Led Aquarium Light.

You can buy it from Amazon Hygger Spectrum Led Aquarium Light.

How does complete darkness affect your goldfish?

Here are the cons of complete darkness in your goldfish tank

1. Your goldfish can suffer from stress 
2. Your goldfish can lose its natural color. 
3. Your goldfish can be unhealthy.
4. It can destroy aquatic plants. 

Stress

Goldfish require a balance of light and dark periods for proper growth and development in their tank. 

If your goldfish gets deprived of light, it can lead to excessive stress and affect the growth of your fish. 

Excessive stress further can also result in the passing away of your goldfish.

Therefore, you should always provide a balance of light and dark periods in the tank to offer them a similar environment as their natural habitat. 

Losing color

Complete darkness 24/7 in the tank can also make your goldfish lose their natural colors as the chromatophores will not produce more pigment, and the new cells are not stimulated to produce pigment. 

So, you will see your goldfish losing their color and appearing drab and pale if your fish is deprived of light.

Therefore, it will be advisable to maintain a healthy alternation between daytime and nighttime to prevent such issues in goldfish.

Also read: Can Goldfish Lose Their Color?

Unhealthy 

Your goldfish gets a balanced light and dark period in their natural habitat. So, in the artificial environment, if you place your goldfish in complete darkness 24/7, your goldfish can turn unhealthy and weak. 

A weak goldfish can further get prone to various diseases and parasites in the tank, eventually leading to significant health issues for your fish. 

So, it will be advisable to provide both light and darkness in the tank to avoid any hindrance to the proper growth of your fish. 

Destroy the aquatic plants

The aquatic plants in the tank play an essential role in keeping the tank well-oxygenated.

Live aquatic plants require light to thrive and for the process of photosynthesis. 

Adequate lighting in the tank will help the plants absorb the carbon dioxide gases your goldfish breathe out and release oxygen to keep the tank well-oxygenated.

In the case of complete darkness, your plants will not be able to function and will get destroyed within 3-5 days. 

Provide natural light in the tank for the proper growth of plants. However, your plants can also grow successfully under the right artificial lights like Led lights.  

So, you should provide a balance of light and darkness in the tank to develop a healthy environment and prevent several issues for your goldfish.

The above were the cons of complete darkness in your goldfish tank.

Also read: Do Goldfish Eat Plants?

Conclusion:

1. Your goldfish cannot see in the dark, so they navigate through their superior sense of smell at night. 
2. Your goldfish has superior eyesight than humans as they can see all three colors(RGB) and ultraviolet, making them sensitive to polarized lights.
3. Your goldfish will not be able to survive for an extended period if you keep them in the dark 24/7.
4.  It would be best to switch off the aquarium lights at night as goldfish are diurnal and rely on a healthy alternation between day and night.
5. Your goldfish can suffer from stress, lose color, and be unhealthy if you keep them in complete darkness. 

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Reference: ScienceDirect ScienceDirect