Lighting Requirements for a Planted Aquarium

Plants, whether they are rooted in soil or submerged underwater, offer a multitude of benefits, particularly in the context of planted tanks or aquariums. They enhance the overall aesthetics by introducing vibrant colors and a diverse range of plant species, creating a visually appealing environment.

Light plays a vital role in the life of aquatic plants, serving as their primary source of energy. To ensure their growth and well-being, it is crucial to provide them with the appropriate lighting setup.

Before diving into the world of aquascaping, it is essential to familiarize ourselves with the various lighting requirements for a planted tank. This knowledge will guide us in creating a conducive environment for the successful cultivation of aquatic plants.

When it comes to aquariums, there is nothing set in stone.
What lighting to use?
What spectrum is good?
How many hours do I have to keep the lights on?

Navigating the complexities of lighting in a planted tank can be overwhelming, especially for beginners. The multitude of factors to consider can easily lead to confusion and uncertainty. However, with a solid understanding of lighting principles, you can confidently make adjustments to your setup that align with your aquascaping goals. Armed with the right knowledge, you'll be able to create the perfect lighting arrangement to bring your vision to life.

Here is a basic guideline for you to get a good idea of lighting for your aquarium:

Proper Tank Dimension

Aquarium enthusiasts often find themselves facing a delightful dilemma when it comes to choosing the right lighting for their tanks. The array of options available can be overwhelming, but it's crucial to select a lighting source that is suitable for the depth of your tank. Deeper tanks require stronger lighting to adequately penetrate the water.

When it comes to tank design, finding the perfect balance between width and length is key. A tank with a spacious back area and a generous front offers you greater flexibility in terms of design possibilities. It's recommended to aim for a width that is approximately half the length of the tank. Similarly, the height can be slightly increased for enhanced visual impact.

If you're unsure about what size to choose, the "20-gallon long" aquarium is an excellent option for beginners. It boasts ideal proportions and a panoramic view, making it easy to set up and maintain. Nano tanks are also popular choices for beginners due to their compact size and simplicity.

The Right Type of Lighting Source

When you're faced with the wide range of lighting options available for your aquarium, it can be overwhelming to make a decision. It's important to familiarize yourself with the primary light sources to make an informed choice.

Let’s have a look at the primary light sources:

  • Incandescent
    • Energy inefficient
    • Uses only 5-10% of the energy for lighting; rest generate heat

    They’re not the first choice anymore. Literally, no point discussing further.

  • Metal halide
    • A powerful light source that produces electricity using halide gas. 
    • Doesn’t take up a lot of space
    • Produces intense heat
    • Demands high maintenance 
    • 25-45% of the energy will produce light
  • Fluorescent
    • The most common light sources in the world
    • Easily available
    • Doesn’t generate too much heat
    • 40-60% of the energy is consumed for lighting 
    • Cheap and energy-efficient making it a great choice for an aquarium
  • LED
    • Rapidly increasing in popularity
    • Energy-efficient
    • Generate less heat
    • Long lifespan
    • Good spread
    • Best for growing plants
    • Check out LED lighting options here

      Considering all these factors, our suggestion would be to choose LED lighting for your aquarium. It provides the best combination of energy efficiency, heat management, and plant growth support.

      Scheduled Lighting

      It's important to understand that keeping your aquarium lights on 24/7 is not beneficial for the health of your plants. To maintain the optimal health of your aquarium plants, it is crucial to establish a proper lighting schedule.

      We highly recommend using a timer system for your aquarium lights. This will ensure that your aquarium receives a consistent amount of light each day. It is best to set the lighting period to around 8 hours. Excessive lighting can lead to plant damage and promote algae growth.

      Achieving a thriving planted tank requires finding the perfect balance between lighting, CO2, and fertilizers. These factors work together to provide the necessary conditions for plant growth and overall aquarium health.

      Adjusted Light Intensity

      A common question that roams at the subconscious of every aquarium owner is, 'Am I providing enough lighting?' or 'how much lighting would be enough?'

      There are no set numbers to answer that question since that depends on your tank’s structure and what kind of lighting you are using. Even so, there are general guidelines you can follow.

      Some use the ratio of the wattage of a light source to the volume [liter] of water to judge whether the lighting is appropriate for the plants. 

      Intensity Required by Plants

      Watts/Liter of Water






      0.8 and over


      An alternative to measuring intensity is lumen. Lumen is a unit to measure light which explains how much light a particular source is providing. Lumen is a better indicator than watts.

      Intensity Required for Plants







      50 and over


      But wait for a second; both watt and lumen aren’t the best indicators for intensity. Watt is outdated as it measures the electricity that is produced, not the output, and lumen takes the sensitivities of the human eye regarding the light spectrum into account. 

      In layman's terms, green will have more lumen value due to human eyes being sensitive to it. However, red and blue light are used more for photosynthesis. So red and blue have less lumen value but are more efficient. Do you see the inconsistency?

      That is where PAR (Photosynthetically Active Radiation) comes to the rescue.

      It records the amount of light available for photosynthesis. The PAR numbers are provided by the manufacturers so you just have to get the suitable one for your aquarium. You can use a PAR meter as well to get a better control over your aquarium lights. 

      The general guideline followed by the community is:

      PAR Value

      Suitable For

      75-100 μmols

      Low light demanding plants

      ~150 μmols

      Medium light demanding plants

      200 μmols and above

      High lighting demanding plants

      You have to make sure enough PAR is produced to balance the depth of the tank. Alongside good lighting, strong tank fundamentals are also necessary.

      If you’re a beginner, starting with a low light/low tech aquarium is the safest as most plants grow in that situation, and it takes less fertilization and CO2.

      Harmonized Color Spectrum

      Plants in the aquarium do use all colors of the spectrum for photosynthesis. However, a red/blue spectrum provides better contrast as it stimulates coloration and displays higher pigmentation in plants, which is why plain white LEDs aren’t suggested in aquariums.

      So, your goal should be to balance the spectrum while highlighting red and blue light. How an aquarium is arranged is also an art, thus aesthetics play a big part. Nowadays, manufacturers publish spectrum charts for their products making it easier for you.

      There’s a secret rule of thumb we can share with you. Experts believe you should let red lights take at least 50% of your spectrum, while blue lights shouldn’t exceed 15%

      The reasoning is that some plants can absorb up to 75% of the total red light being provided, while blue light isn’t needed in too many internal processes of plants. So, this arrangement is an attempt to min-max the situation. 

      You can balance the rest of the spectrum with a color like orange, for instance. Don’t feel bad for green lights as plants would reflect it, and on top of that, human eyes are already sensitive to it. 

      Balanced Spread

      Let’s assume you have invested a lot of time and resources in your aquarium. Although, most of it could be ruined if your spread of the fixture isn’t compatible with the tank’s size.

      A single light source wide bar fixture would create a dispersion pattern and result in shaded areas, even though the PAR rating would seem high.

      To solve this, you can use two or more light sources on a distributed array fixture so that it covers most of the space.

      Visually Enhancing

      Do you think about whether lights can affect the color of your plants? The short answer would be yes, through color temperature. Color temperature plays a good part in how we see the plants. A color temperature of over 8000 degrees Kelvin(°K) would give off a bluish tint, whereas something like below 4000°K would provide a yellowish red tint.

      Color temperature will dictate the clarity of the natural color of the plants. A light source with a high CRI (color rendering index) will result in excellent color recognition.

      It’s important to select lights with proper color temperature, which will visually enhance your aquatic plants.

      Ready To Be a Planted Aquarium Owner?

      By now, you have a better insight into lighting requirements for a planted tank! We are confident that you can make logical and realistic decisions and come up with a spectacular aquarium. Keep those plants lively and graceful. 

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