Light energy is important to all living things be it in water or land. Light in an aquarium enables us to see the beauty of the tank, provides fish and other livestock with light energy whilst for plants light literally gives food as plants use light energy, carbon dioxide (CO2), and nutrients in the water for photosynthesis. Therefore, choosing the most suitable light for a planted tank is crucial but worry no more, by the end of this article you’ll know everything you need to know.

  1. Priority of tank
  • Choose one thing you want to mainly focus on. It could either be plants or fish or shrimps. [This article guides you more on choosing the light for a planted tank]
  • If your priority is fish or other livestock, choosing the best light is rather easier than prioritizing plants.

2. Identify the demand of your plants

  • Aquatic plants are divided into low, medium, and high demand. With that being said, high-demand plants demand or require high or more nutrients, light intensity, and CO2 to grow healthily.
Figure 1

Let’s adapt to compare the lumens (light source produced) instead of a watt (electricity consumed). A fluorescent bulb with the same watt as an LED light may give off lower lumens per litre of water.

NOTE: A simple and cheap way to use the light optimally is by always using a good reflector. It directs all light into the tank or targeted area.

3. Now let’s talk about PAR – Photosynthetically Active Radiation

The PAR Measure (Photosynthetically Active Radiation) is the most helpful check of a light’s vital ‘strength’ for plants development as it directly gauges the measure of light accessible for plant photosynthesis.

Plants utilize apparent light for photosynthesis, which goes from low blue to far-red light and is portrayed as the wavelength between 400 nm and 700 nm. Plants basically use light in the area between 400 nm and 700 nm to drive photosynthesis and are regularly alluded to as Photosynthetically Active Radiation (PAR). Plant scientists measure PAR utilizing the number of photons in the 400-700 nm range got by a surface for a predefined measure of time, or the Photosynthetic Photon Flux Density (PPFD) in the units μmol/s. Photons of various wavelengths are not discriminated by this value.

Figure 2

General PAR guidelines for tank


Figure 3 shows PAR Values at various depths in feet

The light should produce sufficient PAR at the substrate level of depth of your tank. The broad guidelines as commonly used by the aquatic plant community are as follow:

PAR ValuesSuitable for
20 to 30 umol/sLow lighting – suitable for shade aquarium plants such as Anubias, Java fern, Cryptocoryne and mosses. If you are growing these, using low lighting just makes life easier – fewer algae issues because less light means slower growth rates and less maintenance job overall.
~50 umol/sMedium Lighting. You can grow any commercially available plant with sufficient CO2 in this lighting, however, may not achieve the utmost intense colouration in coloured plants. Suitable for carpets. Most carpets grow denser with at least medium levels of lighting.
90+ umol/sHigh lighting – Good for red/coloured aquarium plants. The colouration comes out strongly in higher lighting. Allows for greater density and self-shading effects. However, good control of the tank’s cleanliness and plants health is required to avoid algal issues in this level of lighting.
Figure 4

4. Light Penetration

  • [Water absorbs light] The percentage of light intensity at the water surface is much higher compared to the bottom of the tank as the light gets absorbed by the water from the topper level. Hence, you’ll have to get a strong light (high intensity) to cater to the needs of carpet plants all the way down.
  • Moreover, the height of the light being placed above the tank matters too! The closer the light is placed above the tank, the stronger the penetration at the deepest level is. For instance, if you want to hang your light from the ceiling, causing a huge gap between the light and the tank, then you’ll have to get a very strong light to meet the needs of even low demand plants.

5. LIGHT COLOUR (SPECTRUM)

(i) RGB

  • RGB is an acronym of the LED colours; Red Blue and Green.  Plants can only readily absorb red and blue light and this mixture helps in the leaf and stem development of the plants and used for the absorption of chlorophyll. Therefore, this light boosts the growth of plants. While green light, which is mostly reflected, is more beneficial for your vision.
  • These colours are also used to create moods like nighttime (moonlight) and daytime (sunlight). Not only that, these coloured LEDs gives higher definition hence, enhancing the colours of elements present in the tank such as the rocks, substrate, fish and plants, however, rather dull under plain white LED light.
  • Figure 5 shows live aquatic plants under Chihiros RGB Vivid 2 lighting

(ii) White

  • known for their strengths in energy efficiency. As we know, white light is a mixture of all colours therefore, the emphasis in one particular colour is very weak. This makes the blue, red and green light available for absorption by plants lesser. Even if the strength of light in lumens is higher, plants won’t be able to absorb any light besides red and blue and some green, also, only as much as they require.
  • There are different tones of white light caused by different temperatures measured in unit Kelvin (K). Higher the Kelvin (K), the whiter the light will be hence, the emission of blue tint. Therefore, lower Kelvin (K) gives off a rather orangey-white light. Now, this has NO effects on plants or livestock but merely for the eyes of the observers.
Figure 5 abstracted from hyperikon.com

6. Colour Rendering Index (CRI)

  • it measures how closely a light’s ability is to illuminate an object matching the natural/ideal daylight. The higher the CRI rating of light, the more precisely it renders an object’s colour in daylight.
Figure 6

7. Size of your aquarium tank

Of course, the dimensions of your tank is the basic point to look at when buying a light because you don’t want to fix a light bigger or smaller than the tank.

(i) If light longer than the tank-

  • It cannot be fit neatly thus, needing to hang it.
  • Catering more light energy more than needed by the livestock and live plants in the tank will give rise to algae taking advantage of the excessive light for its growth and multiply aggressively.

(ii) If light smaller than the tank-

  • The light will not be sufficient to cater throughout the tank and meet the needs of the plants.
  • If the tank has less plants focused in the centre then, the area around the centre will appear darker.

8. Aquascaping Style

There are various aquascaping styles and the style you go for will affect the choice of light.

Example 1: The Iwagumi Style – which compromises of only carpet plants, thus, having no tall plants to compete with for nutrients or light, moderate intensity of light is good enough.

Figure 7

Example 2: Island style – for this layout you can opt for shorter lights, don’t concern yourself with the coverage on the sides as there are no plants.

Figure 8

9. Control Panel

  • Nowadays, instead of walking up to your tank every time you want to switch it on or off, you can simply do these controls using a remote as Led Lights of brands like Chihiros come with this function.
  • To top that, Chihiros Led Lights also have Bluetooth settings where you can control the light’s settings using your smartphone. Besides, you can also let the aquatic lives in your tank experience real effects of sunrise and sunset which all can be managed via a mobile app. You only need to pre-set all this once and the light shall function itself the following days based on the settings. Therefore, if you’re a really busy or forgetful person to be monitoring these things manually, then this is the light for you!
Figure 9 shows a snapshot of the MyChihiros app

REFERENCE

Aquasabi.com. 2021. Aquasabi – All about Aquascaping. [online] [Accessed 21 April 2021].

Tropica.com. 2021. The right light for your aquarium – Tropica Aquarium Plants. [online] [Accessed 21 April 2021].

Aquascaping Love. 2021. Aquascaping Styles: Nature Aquarium, Iwagumi& The Dutch Aquarium. [online] [Accessed 21 April 2021].

2hraquarist.com. 2021. How to read PAR tables – The 2Hr Aquarist. [online] Available at: <https://www.2hraquarist.com/blogs/light-3pillars/par_for_planted_tank> [Accessed 30 June 2021].