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How to Choose Lights for Planted Aquarium.

How to Choose Lights for Planted Aquarium.

Posted by Artur Wlazlo on 3 Jan 2023

lants need light. They use it to photosynthesize, creating their own energy to grow and propagate. Without a sufficient level of light, plants cannot photosynthesize and will wilt away. To successfully grow aquarium plants, you must provide a suitable source of light. Lack of adequate lighting is generally the reason why aquarium plants suffer and do not grow well. Choosing proper aquarium lights for plants is probably the most important decision a hobbyist will make, determining how successful he or she will be at keeping aquarium plants.

There are three major features to consider when purchasing aquarium lights: Light Spectrum, Light Intensity, and Light Duration.

Light Spectrum

Explaining what light is and how it works can quickly turn into a confusing disorder of highly technical terms. However, a brief explanation will be helpful as it will later clarify why planted aquarium lights are superior to other lights. The light we see is made up of different wavelengths, each with a specific color. This phenomenon becomes visible to us when we spot a rainbow in the sky. When the sunlight passes through water droplets, it is broken into separate wavelengths and we see them as different colors of the rainbow. These wavelengths are measured in nanometers. For example, blue light is in the 400-nanometer range, green light is in the 500-nanometer range, and red light is in the 650-nanometer range.

Fluval Plant Spectrum 3.0 Bluetooth 24/7 LED

Plants use only some of the light that they receive. Thus, providing the light that plants will use most efficiently should be our focus when choosing lights for a planted aquarium. Plants evolved to most efficiently absorb red light in the 650 to the 680-nanometer range. Plants will also absorb quite well the blue light but strong blue light will also promote algae growth. Accordingly, in the aquarium, we should provide light in the red area of the spectrum.

Modern planted aquarium lights are designed to produce the light that benefits aquarium plants the most. Many also allow you to customize the color output. Shop for the lights that provide the color spectrum needed for your aquarium plants to thrive.

Light Intensity

Light intensity is measured in lumens. By way of comparison, natural bright sunlight produces about 70,000 lux (lux is a measure of lumens per square meter). However, depending on the species, aquarium plants will require anywhere between 300 to 6,000 lux. A lot of the light is lost before it reaches plants. Some light is lost when it is reflected from the surface of the water. Some of the loss occurs when the light passes through water or a glass cover or when particles in the water absorb it. Debris in aquarium water can reduce light intensity quite considerably. The deeper the aquarium, the more loss of light is expected. Keeping a glass cover clean and water clear by removing floating particles from the water with good filtration reduces the loss of light.

Finnex Planted+ 24/7 CRV Aquarium LED Light

Many modern aquarium lights allow you to modulate the intensity of the light, allowing you to customize the light’s output and ensuring that the plants will receive the correct amount of light. This is especially important for larger and deeper aquariums which may require higher intensity to reach the plants on the bottom. Or, conversely, if your aquarium has mostly low-light-tolerating plants like Anubias, these lights will allow you to dial down the intensity and better meet their needs.

Light Duration

In nature, most tropical regions receive between 10 to 12 hours of sunlight. However, the light intensity varies throughout the day with the most intense light occurring during the middle part of the day. To mimic their original environment, the best aquarium lights for planted aquariums come with a pre-programmed dawn-to-dusk light cycle.

These gradual, and more natural, increases and decreases in light intensity eliminate the shock of sudden changes from dark to bright light that both plants and fish would otherwise experience, greatly benefiting their health and well-being. Look for the lights that are programmed to mimic nature and provide for gradual increase and decrease in light intensity.


Fortunately, several aquarium lights available in our online store meet the requirements for planted aquarium lights. One of the most popular lights for a planted aquarium is the Fluval Plant Spectrum 3.0 Bluetooth 24/7 LED aquarium light. The Finnex Planted+ 24/7 CRV Aquarium LED Light and Aquael LEDDY Slim Self-Adjusting Plant Light are also great choices for a planted aquarium. These lights will grow your aquarium plants well and show them in the best light.