Do Aquarium Fish Need Light? (Why + What Kind Of Lighting?)

Image of fish in an aquarium with light

Aquarium fish do need light to differentiate between day and night. Proper lighting helps the aquarium fish regulate their sleeping and eating habits and also enhances their color. Conversely, inadequate lighting makes the fish lose their color and appetite and make them lethargic and ill.

Let’s now see how aquarium lighting affects the fish in more detail.

Why Do Aquarium Fish Need Light?

Fish need cycles of light to determine whether it’s day or night.

Moreover, adequate lighting is essential for their metabolism and overall growth.

This is because fish are usually more active in bright light.

But this doesn’t mean that aquarium lights need to be too bright. Otherwise, fish will start hiding due to intense light.

Proper lighting is essential as it helps bring out the best colors of fish. Also, it keeps the fish active and improves their overall growth.

On the other hand, inadequate lighting results in stunted growth. Fish also lose their appetite and feel lethargic.

What Kind Of Lighting Do Fish Need?

Lighting plays a vital role in an aquarium.

It’s crucial to help plants with photosynthesis and influences fish behavior and physiology.

There are a wide variety of lighting options available in the market.

So you can choose the one that best suits your aquarium setup.

Following are the kind of aquarium lighting that fish need.

1. LED Lights

Aquarists prefer LED lights as they create a shimmering effect, thereby enhancing the overall appearance of the aquarium.

Moreover, they are energy-efficient, have low heat output, are long-lasting, come in varied colors, and you can adjust the light intensity as needed.

2. Full Spectrum Lights

Full Spectrum lights are also called daylight bulbs as they emit light similar to natural sunlight.

They are ideal for planted aquariums as they emit light in all possible wavelengths.

This helps plants with photosynthesis, thereby enhancing their overall growth.

3. Fluorescent Lights

Fluorescent light bulbs or tubes are yet another widely used form of lighting for aquarium use.

They are widely used as these lights are energy-efficient and are available in many types and sizes.

These bulbs work as gas discharge lamps. They apply an electric current to mercury vapors within a tube to generate light.

Fluorescent lights work well in both freshwater and saltwater aquariums.

Moreover, they work with a range of lighting systems, including standard fluorescent, compact fluorescent, VHO, and T-5 HO.

4. Incandescent Lights

Incandescent lights are suitable for small aquariums.

However, they are not used in large aquariums as they produce too much heat.

These bulbs use electricity to heat a filament wire inside to produce light.

These lights are comparatively less expensive than other lighting types.

However, they are less efficient as they last for approximately 1000 hours, which is much shorter than most of the other lighting types and hence avoided by many aquarists.

5. Actinic Lights

Actinic lights are used as additional daylight to illuminate the tank.

They emit a fluorescent blue light that is pleasing to the eye.

Another advantage of these lights is that they are beneficial to plants for photosynthesis.

Best Light Color For Freshwater Aquarium

Full Spectrum white bulbs are commonly used in most freshwater aquariums.

However, they are not very effective, especially if you have a planted tank.

The best light color for aquarium plants is a mix of red and blue as it helps in the leaf and stem development.

Moreover, the colors of aquarium plants pop more in case you have more red and blue lighting.

Another advantage of red and blue lighting is that it’s suitable for plant pigmentation.

Most red plants will grow redder when they get the appropriate nutrients and are exposed to red and blue spectrum lighting.

Along with red and blue lighting, medium green, yellow, and orange spectrum of lighting is beneficial for the visual output of the tank inhabitants.

Now, if we talk about aquarium fish, blue LED lights that are often sold as moonlight bulbs are best for fish.

They also enhance the fish colors, especially the red, blue, and green shades.

Moreover, blue light also gives an ambient and aesthetic look to the aquarium.

Blue light is also beneficial if you have a mix of nocturnal and diurnal fish.

Blue light is not very bright, and so the diurnal fish sleep peacefully while the nocturnal fish venture out and feed themselves.

Another option is magenta-colored lights. This color enhances the red, pink, blue, and green color of the freshwater fish.

It’s also commonly used to create a sunrise and sunset environment in an aquarium.

How Many Hours Of Light Do Aquarium Fish Need?

Aquarium fish follow the same circadian rhythm of day and night as most other living beings on earth.

They need around 8 to 10 hours of light during the daytime. Therefore, it’s better if you match the outdoor light and dark cycles.

You can initially keep the lights on for around 8 hours a day.

Then, if you don’t face algae bloom in the aquarium, you can increase the light to around 10 hours during the daytime.

If you have tropical fish, the ideal hours for light to be kept on is around 12 hours.

This helps recreate the tropical conditions of their natural habitat.

On the contrary, saltwater fish need around 8 to 10 hours of light to simulate their natural environment.

And for cold-water fish, you need to match the seasonal daylight hours with your aquarium lighting as these fish live in aquatic areas with fluctuating daylight hours.

It’s best if you have an aquarium light timer. This way, you don’t have to worry about switching the light on and off every day.

What Happens If There’s Excessive Lighting In The Tank?

Lighting is essential for aquarium fish to stay active and healthy. However, excess of anything is harmful.

Excessive lighting results in algae overgrowth in the aquarium.

Overgrowth of algae makes the tank look unclean, reduce the oxygen level in the tank at night, raise the pH level of the tank water, and block filters, thereby impacting the tank water quality.

Besides, too much light also raises the water temperature, which can prove disastrous to fish.

Excessive lighting is also not suitable for fish, and it can disrupt their sleep.

Fish need darkness to sleep so that they can conserve energy.

Too much light disrupts their sleep and makes them tired and stressed.

Stress further leads to behavioral and health problems such as:

  • Loss of appetite,
  • Weak immune system,
  • Loss of color,
  • Aggression, and
  • Anxiety.

Do Fish Suffer Due To Low Aquarium Lighting?

Adequate lighting is the key to maintaining a healthy aquarium.

But, similar to how excessive lighting is not good, low lighting also harms the fish.

Low lighting makes the fish sluggish, less responsive, and results in loss of color.

Besides, low lighting also increases the fish’s stress levels, resulting in behavioral and health problems.

The effects of low lighting are worse if you have a planted tank.

This is because plants will struggle to photosynthesize in the absence of adequate lighting.

If the lighting continues to be low for a prolonged period, aquarium plants may even perish.

This will result in the depletion of oxygen levels in the tank water.

Low oxygen levels make the fish gasp for air at the tank’s surface.

Moreover, it will lead to respiratory problems, stress, loss of appetite, swimming problems, labored breathing, and other health-related issues.

Related Questions

Do fish need light to eat?

Yes, fish need light to eat, as finding food in the dark is difficult. Most fish have some degree of night vision to swim in darkness.

However, when it comes to eating, fish rely on their senses of smell and sound to find food in darkness.

Moreover, fish depend on their sensory organs to detect water pressure changes that signal nearby food.

Do fish need light during the day?

If the room is well-lit, aquarium fish don’t need extra light.

The primary purpose of aquarium lighting is for the aquarists to watch the activities and behavior of their fish and for the photosynthesis of plants.

Do fish tank lights need to stay on?

Fish tanks don’t need lights to stay on continuously.

Fish need 8 to 10 hours of light during the daytime as it helps them grow faster.

Also, fish need a period of darkness to sleep.

So, it’s ideal for switching the light off at night as aquarium fish follow the same circadian rhythm as humans do.

How long can fish live without light?

Fish can live for around three days without light.

Beyond that, they may suffer and lose their appetite, become lethargic, and may even fall ill.

In addition, some fish like goldfish start losing their color in the absence of sufficient lighting.

Can fish survive without sunlight?

Fish can survive without sunlight. Unlike plants, they don’t need sunlight for biological reasons.

Fish don’t need sunlight if the tank is placed in a well-lit room.

While natural light is suitable for fish, direct sunlight is harmful.

Direct sunlight causes the water to overheat and gives the fish sunburn.

Besides, excessive direct sunlight causes algae to bloom in the aquarium.

However, for some fish like goldfish, sunlight is essential to maintain pigmentation.


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