Planted Aquarium Lighting Calculator

Last Updated on January 18, 2022 by Fabiola L.

Choosing and dosing the amount of light is important for the health of your aquatic world. Click to learn more about planted aquarium lighting calculator.

Light is the most important thing for a planted aquarium. Without it, there is simply no growth or health for your aquatic plants.

PAR, PUR, spectrum, watts per gallon, lumens, kelvins, there are many terms and rules that confuse hobbyists. Troubled by how to choose the right type of light, or worse how to dose it properly? – We are here to help.

Get comfortable and learn all about the planted aquarium lighting calculator.

Types Of Lighting For The Aquarium

We will first discuss the 4 main types of lights suitable for aquarium tanks.


Energy inefficient because it uses only 5-10% of energy for lighting; the rest generates heat. It hasn’t been the first choice in a long time.


It is the most common light source in the world. Cheap and energy-efficient (40-60% of energy is used for lighting).

Metal Halide

This is a powerful light source that produces electricity using halide gas. Namely, 25-45% of energy will produce light.


This energy-efficient type of light is becoming increasingly popular among aquarium hobbyists. It is the best choice for planted aquariums.

Spectrum Of Light – What Is It?

Each plant needs the light of a certain spectrum to thrive, but what is it really?

Light is the smallest amount of energy that can be transported, or as we call them photons. Photons are elementary particles that cannot be split. Thus, they can only be created or destroyed. In addition, they behave like a wave driven by two perpendicular fields. Each of these waves has a different length. Accordingly, we are talking about different types of waves, we are referring to the spectrum.

The type of wave determines the spectrum.

Narrow waves produce only a few types of waves at a time (e.g., only blue and red).

Wide waves produce several types of waves at once (e.g., blue, green, yellow, red, etc.).

Aquarium Lights Spectrum

  • Metal halide light has a fairly wide spectrum.
  • The fluorescent spectrum has a maximum in the blue, green, and red areas.
  • LED lights are basically blue and accordingly produce a fair amount of illumination of the blue spectrum.

Which Spectrum Aquarium Plants Need?

Plants use light to carry out the process of photosynthesis. This in itself is not an easy process and plants need different colors to optimize their growth. The combination of red, blue and yellow, and green proved to be a winning combination for plant growth.

Based on research and comparisons, LED lighting proved to be the most suitable for planted aquariums. This is primarily because it provides a wide and stable color range.

How Much Light For Planted Aquarium

It is important to ensure that the plants in the aquarium get the amount of light they need to be healthy. The amount depends on each plant separately. Most of them need about 12 hours of daylight with 10 hours of complete darkness.

You can use a timer to make sure the “day” and “night” periods are correct. In an aquarium with multiple light sources, it would be good to turn them on and off at different times throughout the day. This will allow a better imitation of the natural daylight cycle.

aquarium lighting calculator

Planted Aquarium Lighting Calculator; Types Of Measures

How Many Led Watts Per Gallon Planted Tank?

The measurement of ‘Watts per Gallon’ originated a long time ago, when basic fluorescent bulbs were used. Today, this type of measurement is considered obsolete.

Furthermore, watts are a measure of power, not light. Accordingly, they tell us how much electricity is consumed in a given period of time. Also, it is very important to emphasize that the light intensity decreases exponentially with increasing distance.

How much light for a planted aquarium? Well, this depends on the specific needs of your plants. This is the simplest planted aquarium lighting calculator (watts and gallons).

Easy plants – 0.25 to 0.5 watts per 0.26 gal,

Medium plants – 0.5 to 1 watts per 0.26 gal,

Advanced plants – 1 watt per 0.26 gal.

Lighting Levels Using T5 Bulbs

Generally speaking, those plants that are considered easy to maintain require 0.25 Watts per liter, medium require 0.50 Watts per liter, and hard difficulty require as much as 0.8 – 1.0 Watts per liter.

In addition, one T5 tube of the corresponding length uses 24 Watts while giving out 1600 lumens of light. This type is very powerful and suitable for growing aquarium plants in densely planted areas.

Lumens Measurement

A lumen is a type of measurement that shows how much visible light the light bulb we see gives. That is, it shows us how much light we are giving our plants.

How many Lumens per gallon?

Low light 40 – 80,

Medium light 80 – 160,

High light > 160.

PAR Measurement

Photosynthetically active radiation (PAR) tells how many photons hit an area of 1 square meter. Simply put, how much energy our plants can use in the process of photosynthesis.

How much PAR is for planted tanks?

Low light <30,

Medium light 30 – 60,

High light> 60.

However, keep in mind that PAR meters tell us about the intensity of light, but not about the quality of the spectrum that light produces.

PUR Measurement

Photosynthetic Usable Radiation (PUR) tells us how many PAR plants can absorb to grow. So if you have 60 PAR in the tank and the plant can only use 50% (30 PAR) of this energy, which means 50% of that energy is wasted. On the other hand, if you have 40 PAR in the tank, the plant will use 75% of that energy and only 25% of the energy will be wasted.

In Conclusion

If you are planning to build a planted tank, it would be good to learn the basics of aquarium lighting. This will save you money and prevent frustrations. We hope you found this article on the “planted aquarium lighting calculator” useful. Let us know in the comments.

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