How Much Light Do Goldfish Need? Important Things to Know!

-- By Carol

Goldfish need about 12 hours of light every day, but that’s not all.

Goldfish also need about 12 hours in the dark every day.

In this article, we will discuss the importance of lighting to keeping goldfish healthy and beautiful, and the best kinds of lighting for your goldfish tank.

Table of Contents

Goldfish Need Light to Stay Healthy

Goldfish need regular periods of light and dark to stay healthy. Every goldfish has a “master clock” in the pineal gland of its brain.

This biological clock schedules digestive processes that allow the goldfish to hunt for food during the day and digest food at night.

It helps goldfish regulate their appetites to keep them from eating too much. It keeps them from becoming dangerously constipated.

This biological clock also programs the retina in the back of each eye to become more or less responsive to ambient lighting.

It helps the goldfish see objects in low light at night and keeps the goldfish from seeing glare in the water around it during the day.

But a goldfish’s biological clock can’t keep time if the fish isn’t exposed to regular, alternating periods of light and darkness.

The lighting in your goldfish tank doesn’t have to match sunrise and sunset exactly, but your goldfish need a 12-hour period of uninterrupted light followed by a 12-hour period of uninterrupted darkness.

It’s OK to keep the lights on over their tank so you can enjoy watching them in the evening, as long as the lights are turned on too early again the next morning.

Goldfish are unlike some other fish and snakes in that they don’t need ultraviolet light or sunlight to make vitamin D.

They get the vitamin D they need from their food.

But they do need a regular cycle of light and darkness to help regulate their metabolism and keep them healthy.

And you need good lighting to enjoy the beautiful colors and playful antics of your goldfish. Here is what you need to know about choosing the lighting for your aquarium.

How to Choose the Best Lighting System for Your Goldfish Tank

The quality of life in your aquarium is directly related to the quality of the light in your aquarium.

The best guide for choosing the lighting system for you goldfish tank is to try to duplicate the conditions that goldfish experience in nature.

The latest lighting technology has made this easy to do.

Fluorescent Lights

Adding the right lighting system to your tank will enable you to see your fish and give your aquarium plants plenty of light for growth.

The lighting system of choice for goldfish tanks use to be fluorescent tube lighting.

There are several reasons fluorescent lighting systems were very popular and still can be used for lighting a goldfish tank.

Fluorescent lights are inexpensive. They won’t heat up and cook your fish.

A fluorescent lighting system for a tank that has only fish and artificial plants only consumes 1 or 2 watts of energy for each gallon of water illuminated.

This is enough light to give your goldfish the experience of alternating day and light conditions.

It will generate enough light for you to enjoy the colors of your goldfish, even those with metallic or nacreous (iridescent) scales.

But if you want to grow plants in your aquarium, you will need 2 to 5 watts of power for every gallon of water in your tank.

Adding live plants to your aquarium doubles or triples your lighting requirements.

It’s easy to buy, install, and maintain fluorescent lighting for your goldfish tank. But LED lighting opens up some possibilities for creative design.

LED Lights

LED lighting is the lighting system of choice for most professional aquarium keepers, and it is also the preference of most people who keep goldfish at home.

This method of lighting uses light-emitting diodes (LEDs) instead of heated filaments like those in traditional incandescent light bulbs or the glowing gases in fluorescent lights.

LEDs are available as lighting strips and lighting tiles. Both of the options are sleek and slim and take up much less space than traditional lighting.

The most useful feature of LED lighting for aquariums is that it gives off abundant light but minimal heat.

This makes them more efficient with lower operating costs. LED lights are also more resistant to the effects of vibrations, power surges, and general wear.

LED lights operate, on average, for 50,000 hours (that’s over 10 years if they are turned off at night), five times as long as the best fluorescent lighting systems.

The fact that LED lights run cooler than older lighting systems also means that you do not need to cool your aquarium water in the summer.

LED lighting is very efficient, so it is possible to use just a few LED units to illuminate even a large tank.

This is one of the reasons LED lighting is better for the environment. LED lights generate only a small carbon footprint.

Even when they wear out, they are better for the environment. LED systems use fewer bulbs and produce less waste.

LED lights can be used in both outdoor ponds and indoor fish tanks. LED lights can be placed close to the surface, so more light reaches the plants and fish below them.

This gives optimum light penetration and better light distribution.

LED lights are also programmable, so you don’t have to turn them off every evening and turn them back on every morning.

They are dimmable, so you can give your fish a variety of lighting experiences, and highlight the colors of different fish you want to view.

You can give your fish a more natural experience of moonlight, sunrise, sunset, and full daylight by changing the settings on your LED units.

If you have plants in your aquarium, you should buy full-spectrum LED lights.

There are also LED lights in blue, magenta, and daylight that can bring out the colors in your fish. You can also change lights to complement the colors in your plants.

Also read: Do LED Lights Cause Algae Growth in Aquarium?

Frequently Asked Questions About Lighting Goldfish Aquariums

Here are some frequently asked questions about goldfish and their lighting requirements.

Q. If I turn off the lights for my goldfish tank in my bedroom at night so I can sleep, won’t they bump into each other?

A. Goldfish can’t see in complete darkness. But complete darkness is a rare condition in nature, or even your bedroom.

There is usually a little light, from moonlight, or from streetlights or other lights in your home.

If you regularly turn off the lights for your goldfish tank, their brains will send a signal to their eyes to make them more sensitive to low-light conditions, as we discussed above.

However, goldfish don’t just navigate by sight.

They have a lateral line system, a collection of seven touch sensors that enable them to detect slight vibrations of other fish swimming in the tank with them.

They also have a keen sense of smell, which enables them to detect familiar landmarks in the tank.

Goldfish are healthier if they get regularly alternating periods of 12 hours of light and 12 hours of low-light or darkness.

But they are not completely dependent on sight to find their way around their tank.

Q. How do goldfish sleep?

A. Goldfish don’t have eyelids, so they can’t shut their eyes when they sleep.

However, goldfish can take short naps during the day and get longer periods of sleep at night by hovering about an inch (25 mm) off the bottom of the tank, preferably under some kind of cover.

They prefer to sleep in a relatively dark, quiet place.

Q. Does lighting outside the aquarium make a difference to goldfish?

A. Goldfish are naturally skittish when they see a potential predator, such as the family cat, through the glass walls of their aquarium.

They learn to get excited when they see the person who feeds them approach their tank.

Goldfish don’t “need” any particular kind of lighting in the room outside their tank.

But they can see what is going on outside their enclosures and respond to people and animals approaching them.

Q. How well can goldfish see? Does lighting make any difference to their quality of life?

A. Humans can see red, blue, and yellow, and colors that are combinations of them.

Goldfish can see all the colors that humans can see plus ultraviolet light and infrared light.

They can see the ultraviolet in the sun’s rays and “full-spectrum” lighting.

What goldfish can’t do is to see very far. Goldfish are nearsighted. They can only see object up to 15 feet (5 meters) away.

This means they can see everything in their aquarium, and they can see you (or your cat) approaching their tank, but they are unaffected by lighting on most objects outside their tank.

Q. Why do goldfish need quiet at night? Can they hear?

A. Goldfish don’t have visible ears, but they have internal ears, inside their heads.

They can hear sound, detect changes in air pressure, and tell whether an object making sound is getting closer or going away.

Goldfish don’t make audible sounds to communicate with each other. As far as scientists know, goldfish communicate with body language.

They cannot communicate in the dark, but that is not a problem, since they prefer to sleep when it is dark.

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