Can Goldfish See in the Dark? (The Answer Might Surprise You!)

My Goldfish aquarium is in my bedroom and I don’t like lights on when I sleep.

But is it the same with Goldfish? Do they like lights on or off during the night? Can Goldfish see in the dark?

I am going to answer all the questions in this article.

Goldfish can’t see in the dark but they have a highly developed sense of smell. They used this sense of smell to swim in a dark fish tank without bumping on each other or tank decorations, etc.

Goldfish are also equipped with a Lateral Line System (LLS) which is basically a group of sense organs that gives them the ability to detect even a slight movement or vibration in the water that helps them for defense and navigating through a dark fish tank.

Can Goldfish See in the Dark image

Can Goldfish live in the dark?

In their natural habitat Goldfish needs to protect itself from predators. That’s why they have developed lateral line organs which is basically a group of sense organs that allows them to protect themselves and also to navigate in the dark.

There is also a slight fade in their color during the night when they sleep that helps them to hide from the predators. Overall Goldfish can easily live in dark.

What happens when you put a goldfish in a dark room?

As mentioned above goldfish can easily live in dark. But like us, goldfish require light too to maintain their natural cycle.

In their natural habitat, Goldfish stay active during the day, eat food and at night they sleep.

So to emulate their natural cycle in the artificial aquariuum you should keep the lights of your aquarium on for 12 hours and off for 12 hours.

How do Goldfish sleep?

Goldfish like to sleep when there is dark and quiet. So usually Goldfish sleep at night when there is dark and quiet.

Some Goldfish take a nap during the afternoon and some don’t sleep until night.

Goldfish don’t have eyelids so their eyes are open when they are sleeping. 

They hover about 1 inch above the bottom of the tank and their head is slightly tilted downside when they are sleeping.

You can also notice a slight fade in their color when they sleep.

Goldfish like to sleep in the dark, so you should keep the lights of your aquariums off during the night.

You should not keep the lights of your aquarium on for more than 12 hours.

Also, make sure that there is no sound source near the aquarium during the night.

Watch Goldfish Sleep!

Can goldfish see outside the tank?

There are a lot of mixed opinions about it. But Goldfish has good eyesight. They get excited when they see their owner and entice to feed them. 

Also, when you put your fingertips on the tank they usually try to nip it, considering it a food. 

On this behavior, we can conclude that fish can see outside the tank. 

Though there is no research done on this topic as far as I know.

How well can a goldfish see?

Goldfish have very developed eyesight. In some respects, they have superior eyesight than us. 

Humans can see only three colors and their combinations red, yellow and blue.

But goldfish can see four colors that enable them to see infrared light and ultraviolet light and they are the only ones who have the ability to do that in the whole animal kingdom.

But their eyesight is not all great.

They can clearly see about 15 feet only and their depth vision is poor. For most fish everything after few feet is a bit unclear.

Their eyes are located at the side of their head that creats a big blind spot right in front of their nose.

Some variety of fancy Goldfish like Telescope goldfish have poor vision (What an irony!)

Can Goldfish hear?

We all know that Goldfish do not have ears. But can a Goldfish hear us? 

Surprisingly the answer is yes. Do we don’t see ears of a Goldfish but they do have internal ears inside their head that allows them to detect sound particle, motion and the detection of sound pressure.

Can Goldfish talk:

Fishes can communicate by making noises like grunts, chirps, and pops.

Goldfish have a very good hearing capability but they can’t make any noise or sound. Instead, they communicate through body language. 

Quote by University of Auckland marine scientist Shahriman Ghazali

Do Goldfish grow

According to DEC when Goldfish are kept in a small aquarium or fishbowl they don’t grow more than 6 inches.

But goldfish found in wild and pond can grow up to 12 to 14 inches in length.

But the longest Goldfish is about 18.7 inches long which was found in the Netherlands.

And the second-longest Goldfish is goldie which is about 15 inches long.

When the owner bought Goldie home, it was about 1.2 cm but over 15 years it grew to 15 inches long.

Goldfish can live 15-20 years but it’s not very common. Usually, Goldfish live about 10 years.

The growth rate of Goldfish is really depends on the environment. If you manage to maintain a healthy environment for Goldfish then it can live longer.

How to maintain a healthy environment for Goldfish growth?

factors affecting goldfish growth infographic
factors affecting goldfish growth infographic


Goldfish are cold-water fish so you should maintain low water temperature in your Goldfish tank.

The ideal temperature for Goldfish is 65 degrees Fahrenheit to 75 degrees Fahrenheit.

High water temperature can cause permanent nerve damage to Goldfish.

There are a few things you can do to maintain low water temperature in your Goldfish aquarium.

  • If you noticed the high temperature in your Goldfish aquarium then you should immediately turn off the aquarium lights and remove its lead.
  • You can put a table fan near the aquarium tank in such a way that the water will flow over the surface of the tank.
  • Take some ice cubes packed it into a zip-closed bag and hang it inside the aquarium.
  • Move your aquarium if it is directly exposed to the sunrays. The sunrays can increase the temperature in your aquarium.

Also, Goldfish are very messy fish i.e. they produce a lot of waste so you should have a good filtration system for your Goldfish.

You should use a powerful hang on the back filter or if you have a budget then you should go for a canister filter.


You should feed 2 to 3 times a day to your Goldfish.

Goldfish are omnivorous so they eat both vegetarian and non-vegetarian foods.

You can feed them various vegetables like peas, spinach, broccoli and fruits like Orange, Apple, etc to fulfill their vegetarian diet.

For non-vegetarian diet, you can feed them flakes and pellets small insects and worms.

Bread is commonly fed to the fish but it is not good for them. If you run out of food then goldfish can wait until you get the food. They can live without food for a long time. Just don’t feed bread!

Tank size

The tank size also plays a very important role when it comes to the proper growth of a Goldfish.

Goldfish cannot grow in a small tank for fishbowl.

It will get stunted that is it will not grow if you keep it in a small aquarium or fishbowl.

20 gallon per Goldfish is a good rule of thumb to follow.


Maintaining a healthy amount of oxygen levels in your aquarium is also very important for the proper growth of your Goldfish.

How much oxygen your fish needs really vary but according to FWS 5 parts per million PPM of dissolved oxygen or higher is good for fish.

Signs of low oxygen

  • If you noticed your Goldfish coming on the surface of the water and gasping for air frequently then it is a sign that your aquarium has a low oxygen level.
  • If you found your Goldfish less active then chances are your aquarium has low oxygen.
  • If you noticed the rapid movement of gills and labored breathing in your Goldfish then your Goldfish is getting an insufficient amount of oxygen.
  • When Goldfish get less oxygen then it also start to eat less.

Ways to increase oxygen in your fish tank

  • If you noticed any of the above signs then your aquarium has low oxygen levels and to increase oxygen in your aquarium you should immediately pour down some water of your aquarium using a jar or pitcher from some height.
  • You can also do a large water change of about 50% of your tank to increase oxygen in your aquarium. The freshly introduced water will have more oxygen than the existing.
  • If you are facing low oxygen level problem during power cuts then you can use a battery-powered air pump to continuously provide oxygen during power-cuts.
  • You can use a hang on the back filter to increase the oxygen in your aquarium. The water falling from the filter will get exposed to the air which helps to oxygenate the water.
  • If you have a spray bar then this is the right time to use it. Using a spray bar will help water to get exposed to the air which will oxygenate the water.
  • The simplest and most reliable way to increase oxygen in your aquarium is to use an air pump. (Check out our Air Pump recommendation)
  • If you notice a low oxygen level in your pond then using a fountain is a great way to oxygenate the water in your pond.

Causes of low oxygen

  • Overstocking is the most common reason for low oxygen in the aquarium.
  • If the water temperature of your aquarium is high then this causes low oxygen level in the aquarium because high-temperature water holds low oxygen than cold water.
  • If you are using any kind of chemical for medications then this could be the reason your aquarium has low oxygen.
  • If you have live plants in your aquarium and if it’s not getting a sufficient amount of light then the plants will produce carbon dioxide instead of oxygen which will ultimately decrease oxygen level in your tank.
  • Lack of water movement also causes low oxygen levels in the aquarium.


So Goldfish cannot see in the dark but they have a developed sence of smell that helps theym to navigate in the dark aquarium or pond. 

They have a Lateral Line System which is basically a set of sense organs that helps them to navigate in the dark.

In their natural habitat, this set of sense organs also helps them in defense.

Photo of author
Prathmesh Gawai
He is the main author and editor at And he loves to share helpful information on aquarium and/or fishkeeping hobby. Prathmesh has over five years of aquarium and/or fishkeeping experience. Currently, he has a Betta fish tank. He has written hundreds of articles on various aquarium fish species and on fish tank maintenance over the last five years. Connect with him on YouTube here. Learn more about him here.

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