Should A Fish Tank Light Be On All The Time?

Nick Durante
by Nick Durante
Credit: Shutterstock / Solarisys

It can be stressful to take care of a fish tank, whether you’re experienced or a novice when it comes to the hobby. Everything from the substrate, plants, food, and lighting can affect the health of your fish. So, should a fish tank light be on all the time?

A fish tank light should not be on all the time, and 8-12 hours is enough for your fish and plants. Fish don’t naturally get more than 6-8 hours of sunlight per day in many natural habitats. You can cause an algae overgrowth if you leave the lights on in your tank for 24 hours per day.

The algae can harm your fish, pull oxygen from the water, and take a while to control. Full spectrum lights and neutral white lights are best for most fish tanks. Follow along as we explore how long you should keep a fish tank light on and highlight why lighting matters.

How Long Should You Leave A Fish Tank Light On?

Ideally, you should leave a fish tank on for at least 8 hours per day. That said, many people run the light in their fish tank for 10-12 hours or longer. It’s important to research the light requirements for the type of fish you have in your tank based on their habitats.

Some fish tanks may only need as little as 6 hours of light each day. Many types of fish won’t get nearly that much sunlight in nature. Fish often get indirect nature in the wild, but it depends on where they are from.

Because of that, there’s no reason to overexpose your fish to light in the tank. The light is ultimately more important for the plants in your tank.

Why Do Fish Tanks Need Lights?

Fish tanks need lights to help create a healthy day and night cycle for your fish. They also increase visibility, so you can easily keep an eye on your fish. That said, most fish don’t need lights in a tank to survive, but it’s still a great idea to use at least one.

Lights are essential if you put plants in your fish tank, and most hobbyists consider that important. Plants add depth to your tank and give your fish more chances to exercise and have fun. You can also increase the oxygen in your fish tank if you add plants and a great lighting setup.

You can probably tell the difference in your fishes' behavior when you turn the light on or off in your tank. Some fish become more active in the dark, while others become mostly idle. This behavior difference is important for their energy levels, digestion, and exercise requirements.

Can You Leave A Fish Tank Light On All The Time?

You shouldn’t leave your fish tank light on all the time. This will put your tank at a huge risk for algae, and that can harm your fish. Algae can eventually consume the oxygen in your tank that your fish need to survive.

Excessive light in your tank can also affect the way your fish behave. For example, you may wear your fish out if you keep the light on for up to 24 hours. The lights in your tank can energize your fish, but it becomes too much when they stay on all the time.

Fish rely on day and night cycles to experience full lives. You can also damage the plants in your tank if you leave the light on all the time. Strong beams of light can stain a plant’s leaves white in some cases, especially if the light is too close.

Can You Use Any Light For A Fish Tank?

You can’t use just any light for a fish tank, as some are too bright, dull, or blue. Ideally, you should look for 5,000-6,500 K lights for your tank. Those provide light that is close to what the fish would encounter in their natural habitats.

Some people install standard LED lights in their fish tanks, but that doesn’t always work. Standard LED lights aren’t designed to withstand the conditions within a fish tank. The humidity can damage many types of LED lights, and they may go out quickly.

Neutral white lights are great for fish and plants within tanks, but some people prefer blue lights. Slightly blue lights encourage activity from fish and can help your plants grow. Otherwise, it’s worth installing a full spectrum RGB light to provide the perfect light balance.

Is Natural Light Enough For A Fish Tank?

Natural light is only safe for a fish tank if it doesn’t affect the temperature too much. Direct sunlight can harm the fish in your tank if the water becomes too hot. The ideal temperature for most fish tanks is 75 to 80 degrees Fahrenheit.

Your tank may quickly reach the maximum temperature in direct sunlight, and that can upset your fish. Not only will it stress them out, but it will also affect their health. They will breathe more oxygen and the excessive heat will increase their metabolism.

Eventually, the fish will lose energy and they may even stop eating. Make sure to keep an eye on the thermometer in your tank if you use natural light. Your tank may be safe if the tank is far enough from a window, but it’s a hard balance to find.

Can Your Fish Handle A Day Without Light?

The fish in your tank can handle a day without light. However, they may experience metabolic and behavioral changes in total darkness. For example, this can happen if the power goes out and your tank is in a room without windows.

Otherwise, your fish should be fine if the lights go out and they still get natural light from the sun. That said, you must check the thermometer to make sure the water isn’t too warm. You can easily lower the temperature if you add some cool water to the tank.

The plants in your tank may suffer if they go a day without light. It shouldn’t be enough to kill them, unless they are already in trouble. Luckily, your plants should bounce back as soon as you can turn the lights back on.

Summing It Up

You should only keep a fish tank’s lights on for 8-12 hours per day for the best results. Otherwise, your fish may experience metabolic problems and suffer from low energy due to excessive light. Look for full spectrum lights or neutral white lights for your tank to encourage healthy behavior and growth from your fish and tank. Regular LED lights can work, but the humidity may break them.

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Nick Durante
Nick Durante

Nick Durante is a professional writer with a primary focus on home improvement. When he is not writing about home improvement or taking on projects around the house, he likes to read and create art. He is always looking towards the newest trends in home improvement.

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