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lighting requirements for a planted aquarium

Lighting Requirements for a Planted Aquarium


Written by: Anne (


Be it planted in the ground or underwater, plants always are on our side. They bring a bag full of benefits, especially when it comes to planted tanks or aquariums. They are aesthetically appealing by adding color and variety as well as improving the surroundings.

Light is life for aquatic plants. It is their bread and butter. So, in order to provide them with a healthy atmosphere, we need the right kind of lighting setup for their growth and well being. 

There are several lighting requirements for a planted tank that we need to know before jumping straight in to aquascaping... and that’s exactly why we are here.

 aquarium lighting

Aquarium Lighting 101

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?

There are many things to consider when answering these questions. So, it is pretty easy to get lost in decision making. As a beginner, such calculations can leave you puzzled. With the correct knowledge of lighting, you can tweak your arrangements to suit your aquascaping wishes. 

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

Proper Tank Dimension

This is where aquarium hobbyists have to face a sweet dilemma. There are so many options to choose from. Regardless of what you prefer, make sure your choice of lighting source is adequate according to your tank's depth. The more depth your tank has, the stronger the lighting source is required. 

An aquarium with a broader back area and a large front offer you good versatility to play around with the design. You need an excellent harmony of width and length to work with.

The width should be half the length of the tank. The same goes for height (sometimes people add extra few centimeters for a better optical effect).

If you are undecided on what size to pick, the “20 gallon long” is an ideal entry-level aquarium with perfect proportions and a panoramic view that is easy to set up. Nano tanks, such as the UNS 5S or 5N are the perfect beginner tanks as well.

Click here to see a wide array of rimless aquariums.

aquarium lighting

The Right Type of Lighting Source

When you go to purchase some lights, you will see a wide range of products which may confuse you. A smart buyer would try to learn about them beforehand, but even that is overwhelming at times. So, what do you want to pick?

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 ⭐
  • Our suggestion would be to pick LED lighting. There is no better alternative to LED for planted aquariums at the moment. It is the best pick of the lot.

    aquarium lighting

    Scheduled Lighting

    Using lighting in an aquarium doesn’t mean you keep the lights on 24/7; that’s detrimental. To keep your plants inside the aquarium healthy, you need to switch your lights off and on at the right time.

    We recommend setting up a timer system because it will help your aquarium get an equal amount of light every day. Set up your lighting period for 8 hours at best. Anything more is a recipe for disaster since you will scorch your plants and give birth to algae.

    You need to find the perfect balance among light, CO2 and fertilizer to achieve a thriving planted tank.

    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

    aquarium lighting


    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. 

    aquarium lighting


    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.

     aquarium lighting ONF

    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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    Shannon Pardy - June 12, 2024

    Thank you so much for explaining this. I’m having trouble getting my tank plants to grow, but after buying a LED color-adjustable light, I was drowning in info, but none of it was helpful! There was nothing in google searches about how much for a 30g tank, how much red, blue, green, etc. Your article answered every question I had!

    Jason Stathum - February 26, 2024

    Great article! Your detailed guide on lighting requirements for a planted aquarium is incredibly informative. I’m always curious about lighting in aquariums, and your blog has been my go-to resource. I appreciate your expertise! By the way, I’ve also been exploring Caterlux for valuable insights on LED lights. Keep up the excellent work!

    Ted Freed - July 6, 2023

    Everyone talks ad infinitum about lighting issues without saying anything about the requirements of specific plant varieties. Hence, fairly useless info.

    Tobin Lewis - December 8, 2022

    A very thorough article. Thank you for taking the time to put it together.

    Alejandro Lee - December 7, 2020

    Thanks! Just in time. I am looking for LED lights.

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