Do Goldfish Need A Light? (Why Lighting Is So Important)

Last Updated on 2023-08-05

If you’re wondering whether goldfish need a light then you’ve found the right article! In this article, we’ll be exploring whether or not goldfish require a light and the various factors to consider when deciding whether or not to light up your aquarium. 

So keep reading to find out everything you need to know!

Do Goldfish Need A Light?

Goldfish need a light for proper growth and color enhancement. With no light in their tank their circadian rhythm will be out of sync which will stress them. Aim to give your goldfish 12-14 hours of light per day, and 10-12 hours of darkness.

In nature, goldfish would likely receive exposure to daylight and therefore experience natural cycles of day and night, with periods of darkness. This same pattern can be replicated in captivity by using a timer on an artificial light source.

Providing some form of illumination can help your fish regulate their sleep and eating patterns, making for a happy and healthy home for them.

Benefits Of Having A Light In A Goldfish Tank

Having a light in their tank can provide several benefits for your goldfish and their health

1. Regulation Of Circadian Rhythm

Having a consistent day and night cycle can help regulate your goldfish’s circadian rhythm, which is needed to let them know when they should sleep, when they should wake, and when they should eat.

2. Plant Growth

If you have live plants in your goldfish tank, a light can help promote their growth and photosynthesis. Without light, your plants will begin to wither and die. However, if you’re using sunlight to light your tank, then you may end up with an algae issue.

3. Aesthetic Appeal

And of course, a light in the aquarium can enhance the beauty of your goldfish tank, providing a visual appeal and allowing you to enjoy the fish in their natural environment.

How Much Light Does Goldfish Need?

Goldfish need around 12-14 hours of light per day, and 10-12 hours of darkness a day. While you can fluctuate a little bit with this. If they’re not getting enough light, they may start to turn pale.

On top of this, a consistent day and night cycle can help regulate their sleep patterns, feeding times, and overall behavior. Goldfish are exposed to natural sunlight and darkness in the wild, so it’s essential to provide a similar environment in their aquarium.

If you have an aquarium light in your aquarium try the following! During the day, a brighter light can be used to simulate natural daylight, while a low light or moonlight effect may be sufficient at night since goldfish are not very active during those times.

If you have live plants in your aquarium, they require a certain amount of light for photosynthesis and growth too. In this case, you should provide 12-14 hours of light per day, depending on the type of plant. As most plants require more light than goldfish.

And lastly, choosing the right type of light for your aquarium is important to ensure that your goldfish and plants receive the appropriate amount of light.

(If you haven’t added plants to your tank yet, check out some of the best red plants you can choose!)

Can Goldfish Get Too Much Light?

Goldfish can get too much light. While some artificial light can be beneficial for helping your fish establish natural sleep and eating patterns, it’s important not to run the lights for more than a few hours each day. 

Here are the things that will happen if your goldfish get too much light:

1. Algae Overgrowth

One of the most common issues that occur when goldfish get too much light is the rapid growth of algae in the tank. Goldfish require a certain amount of light for their health and growth, but excessive exposure can cause algae to bloom.

 Algae overgrowth can quickly cover the water’s surface, the tank walls, and even the plants, making it difficult for goldfish to swim and breathe. Additionally, too much algae in the tank can cause water quality issues, leading to the growth of harmful bacteria and viruses.

(Some of the most common algae you can expect in your tank are green hair algae, green spot algae, blue green algae, brown algae, white algae, and red algae!)

2. Increased Water Temperature

Another issue that can occur when goldfish get too much light is increased water temperature. The light produces heat, which can warm up the water in the tank. If the water temperature rises above the recommended range, it can cause stress to your goldfish and even lead to their death.

(If you’re fish keeping dying here are all the reasons.)

Additionally, if the warm water is too hot, it could end up causing temperature shock in your goldfish, which can kill them rapidly.

3. Poor Water Quality

Too much light can cause poor water quality in the tank, harming your goldfish as well.

Algae overgrowth and increased water temperature can decrease oxygen levels, and cause pH fluctuations in your tank decreasing the quality of the water. Poor water quality can stress your goldfish, weakening their immune systems and increasing their susceptibility to infections and diseases.

4. Stress

Excessive exposure to light can cause stress to goldfish, leading to health issues such as weakened immune systems and decreased appetite, most likely due to lack of sleep. In rare cases too much light can cause damage to the retina, leading to permanent blindness.

Goldfish constantly exposed to bright light can also become stressed, leading to decreased activity levels and reduced lifespan.

What To Look For When Choosing A Light For Your Goldfish?

A good light not only enhances the appearance of your goldfish and plants but also helps maintain their health and well-being. Here’s what to look for when choosing a light for your goldfish.

1. Size Of The Aquarium

The size of your aquarium will determine the size and wattage of the light you need. A larger aquarium will require a larger light to adequately illuminate the tank. If you have a small aquarium, a compact fluorescent bulb or LED light may be sufficient, while a larger aquarium may require a more powerful light.

2. Type of Light

There are different types of lights available, including LED, fluorescent, and incandescent. LED lights are a popular choice for aquariums as they are energy-efficient and long-lasting. They also produce less heat, which is important as you already know, too much heat can be harmful to your fish. Fluorescent lights are also a good option as they provide a full spectrum of light, making them ideal for promoting plant growth. 

On the other hand, incandescent lights are not recommended for aquariums as they generate too much heat and do not provide adequate light.

3. Spectrum of Light

Goldfish require a specific spectrum of light to thrive. Look for a light that provides a spectrum of light that includes blue and white light, as this will help promote plant growth and enhance the colors of your fish. Avoid lights that are too yellow or red, as these can create a dull and unappealing environment for your fish.

(Find out just how important blue light is for your fish!)

4. Duration of Light

Remember it’s important to provide your goldfish with a consistent amount of light each day. Most aquariums require 12-16 hours of light per day. You can set your light on a timer to ensure that your fish get the right light each day. If you have live plants in your aquarium, you may need to provide more light to support their growth.

5. Heat Emission

Some lights can generate a lot of heat, which can increase the temperature of your aquarium. Look for a light that produces minimal heat to avoid negative impacts on your fish and plants. LED lights are a good choice as they generate less heat than other types of lights.

6. Budget

The cost of lights can vary widely, so it’s important to consider your budget when selecting. Keep in mind that a higher-priced light may be more energy-efficient and last longer, which could save you money in the long run. If you are on a tight budget, you can opt for a basic LED light or fluorescent light.

What Color Light Is Best For Goldfish?

Goldfish are naturally attracted to bright colors, so it’s important to take this into account when selecting the right light for your aquarium. The ideal lighting for these aquatic pets should provide both broad illumination and visibility without emitting too much heat or being too intense.

1. Bulb Color & Color Temperature

When choosing bulbs for your tank, remember that color temperature is measured in Kelvin (K) – with higher temperatures corresponding to a warmer hue and lower temperatures representing cooler tones. Generally speaking, fluorescent lamps generate a cooler tone closer to 6500K and LEDs can range from 3000K (warm white) to 10,000 K (cold blue).

However, both offer several choices in between, so you can usually find something that suits your fish’s needs!

2. Different Colors of Light Have Different Effects

Cooler lights tend to bring out the reds, oranges, and yellows in your fish, while warm lights produce more vibrant colors – adding contrast to their scales, fins, and other features. Additionally, some colors, such as blues or purples, can be calming influences on some varieties of goldfish; however, use these sparingly as too much could inhibit activity levels.

3. Avoid Natural Light

You may think that natural light will do, and while in itself it’s probably good for your goldfish, it’s not ideal for your tank. Depending on where you live natural light may end up heating your tank up too much, and it will definitely increase the amount of algae you find in your tank too!

(How to deal with algae in your tank naturally if you already have too much.)

What Happens If You Keep Your Goldfish In The Dark?

If goldfish are kept in the dark for an extended period, they may experience a number of negative consequences. These include:

1. Disorientation and Difficulty Finding Food

Without adequate light, goldfish may become disoriented and have difficulty finding their food. This can lead to malnourishment and even starvation in severe cases.

2. Stress and Reduced Immunity

Goldfish rely on the light-dark cycle to regulate their stress response and immune system. When this cycle is disrupted, the fish may experience chronic stress and reduced immunity, which can make them more susceptible to disease and other health problems.

3. Poor Sleep Quality

Goldfish, like humans, require adequate sleep to maintain their health and well-being. When kept in the dark, goldfish may experience disruptions to their sleep cycle, which can lead to poor sleep quality and other health problems.

(Want to know more about how exactly goldfish sleep?)

4. Faded Colors

As mentioned earlier, goldfish rely on light to maintain their vibrant colors. Without adequate light, their colors may become dull and faded over time. Did you know in some cases, a goldfish that doesn’t get enough light can even start to turn black.

Should I Turn My Goldfish Light Off At Night?

Generally speaking, it’s a good idea to turn your goldfish’s light off at night or at the very least swap it to blue light. If bright light is constantly shining in your goldfish’s tank it will stress them out and damage their immune system.

Here are the pros and cons of turning your aquarium light off at night and whether it is beneficial or harmful to your fish.

Benefits of Turning Lights Off at Night

  • The most obvious benefit to turning lights off during the night is that it will give your goldfish an opportunity to establish a natural sleep/wake cycle, which helps them stay healthy by allowing them restful periods. Never forget goldfish require around 10-12 hours of light and 12-14 hours of darkness per day to ensure their internal clock is properly regulated. 
  • Additionally, if the light is too bright for your goldfish during the day, then having some amount of darkness can be beneficial in helping reduce stress on their eyes.

Thankfully, some fish tank lights come with a timer feature that allows you to automate the light cycle, which can be helpful in ensuring your goldfish receive the appropriate amount of light and darkness.

Do Goldfish Fry Need Light?

Goldfish fries require special care and attention in order to thrive. One important factor to consider when caring for goldfish fry is whether or not they need light, as well as how much should be used.

Goldfish fry need light just as much as goldfish themselves. It will help them grow, and as long as there are no predators in the tank that will eat them, you won’t have to worry about the light opening them up to danger.

Light Requirements for Goldfish Fry

Generally, it is recommended that you provide some form of illumination during both day and night periods in your aquarium setup – either with lamps or windows – to ensure the best health conditions for your goldfish fry.

The intensity of the lighting should be low; this could come from a low-powered lamp or natural sunlight from windows (depending on where you keep your aquarium). This allows their retinal cells to develop correctly – without adequate illumination levels, they will eventually become blind over time.

Impact of Too Much Light on Goldfish Fry

It is also important to note that too much light can have adverse effects on the wellbeing of your fish fry. Excessive lighting can cause stress to them just like adults and weaken their immune system. If you notice any behavioral changes in your fish, such as hiding more often or listlessness, it’s likely that the level of lighting was too high and needs adjusting accordingly.

Is Sunlight Good For Goldfish?

If you’re still thinking about sunlight for your goldfish then it’s important to remember a few things.

Sunlight is good for goldfish themselves as it helps their circadian rhythm. However, too much sunlight on a tank can cause the tank too heat up too much and increase the algae in your tank. The former is dangerous, and the latter can be frustrating.

Types of Sun Exposure

When introducing sunlight into an aquarium setup, there are several factors to consider, such as type, intensity, and duration. Natural sunlight from windows is usually the preferable option; however, if this isn’t available, artificial light sources such as full-spectrum bulbs can be used instead in moderation.

Just be sure that when using these types of lights that the intensity isn’t too bright for your goldfish.

Too Much Sunlight Can Be Harmful

As beneficial as exposure to natural or artificial sunlight can be for your goldfish, too much sun can also prove harmful. Prolonged periods in direct sunlight can result in the tank water evaporating quicker, and the tank becoming too hot.

Do Goldfish Need A Light_ (Why Lighting Is So Important)


Here are some frequently asked questions that people have about whether or not their goldfish needs light.

Do Goldfish Like Blue Light at Night?

Goldfish typically prefer blue light at night, as the wavelengths are similar to the moonlight they experience in the wild. Blue light helps goldfish regulate their day/night cycle and reduce stress levels, allowing them to get a better quality of sleep.

Do Goldfish Like Colored Lights?

Goldfish seem to enjoy the colors of light that shine in their aquarium or fish tank. The colors can be soothing and provide a fun, decorative element to their environment. Goldfish have even been known to chase the light when it is moving around the water!

Some owners have reported that their fish become more active and alert when exposed to certain colors.

Can Goldfish Live in Darkness?

Goldfish can survive in near-total darkness for a short time. Long periods of complete darkness can cause stress to them, however, as well as their circadian rhythm and biological clocks. They tend to become sluggish and unresponsive when living in long-term dark conditions.

To ensure the health of your goldfish, provide them with a source of low-level light for at least part of their day.

Do Goldfish Need a Heat Light?

Goldfish do not require a heat light, as they are comfortable in cooler temperatures more than most other fish. They generally prefer an aquarium environment with temperatures between 65-72 °F. An aquarium heater is still recommended to maintain a consistent water temperature in the event of power outages or changes in temperature due to seasons.

(Find out how important a heater really is for your goldfish.)


In conclusion, providing a light for your goldfish is not necessary for their survival as long as they’re getting some form of natural light, but it can greatly improve their overall health and well-being.

A consistent light cycle can help regulate their internal clocks and promote healthy behavior such as feeding and sleeping. So, if you’re looking to create a happy and healthy environment for your aquatic friends, consider adding a light to their tank!

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