A common question comes to mind during setting up a planted aquarium is how to pick the best aquarium lighting? There are few factors that would determine the right light for your planted aquarium and without wasting any time i would dig straight into it. 

1. Spectrum of Aquarium Light:

Aquarium light can come in different spectrum and in my opinion it doesn't have much affect on the growth of plant. It is up to the hobbyist what light they pick for the aquarium based on their own personal preference. A warm white light can give the tank a yellowish color, however cool white light can turn the fish tank bluish. Plants can thrive under any light spectrum as long as it is not too bluish like lighting for a coral reef tank. 

Most of the aquarium hobbyist go for a neutral white light because it simulate natural daylight. A 'K' rating is not an indicator of light suitability as it only measures the visual color of lighting affect in the planted tank. An aquarium light with 6500k is sometimes labelled as daylight by the manufacturer and is known by the term "Full spectrum". All white lights contain RGB (red, green, blue) wavelengths of light by default and can be called full spectrum lighting. So what matters the most? Keep on reading this article to find out.

2. Strength of Aquarium Light:

Light intensity can be classified as one of the main factor in growing aquatic plants which is measured in PAR. Photosynthetically Active Radiation is considered as the most accurate measure of strength of light for aquarium plants. However, in most instances PAR table is not provided by manufacturer. In such case, Lumens can be used for LED lighting and Watts for fluorescent lighting. Light brightness as measured by Lumen can sometimes get misleading as high lumen doesn't guarantee high levels of red and blue. It must be noted that human eye is more sensitive to green and plants require red and blue for photosynthesis, so a high lumen light which is red and blue heavy would be great for a planted tank. 

As discussed earlier (in spectrum of aquarium light), it won't affect the growth of plant too much but i thought i should discuss in bit more detail here if you take everything into consideration. Fluorescent lighting is measured in watts, however, most packaging usually tells how many watt the aquarium lighting will use and not how much wattage will be produced. Most of the time fluorescent lighting produces excess heat energy rather than light energy which is useless for the growth of plants in the aquarium. Pay more attention to the packaging and find out how many watts of light is produced by the fluorescent lighting. 

LED lighting is energy efficient and it uses less electricity and generates more brightness. Hobbyist are better off getting LED lighting as most of them come with added options such as controlling light spectrum and light intensity through extra gadgets. They can also imitate the gradual sunrise and sunset seen in nature. Beginners usually comes across the issue of high algae growth if a high strength light is used in the tank which can be brought under control by managing other parameters in the tank and also by dimming the light intensity of LED aquarium light when required.

3. Spread of Aquarium Light:

The second most important factor is how far the light is spread in the aquarium. Most of the aquarium lighting is dispersed roughly around 1 foot directly below it. It means all the plants in the corner or at the front or anywhere not directly underneath the light will potentially miss out. You might have noticed that when you add small plants in the tank, they grow well in the start. However, after gaining some height, bottom leaves starts to fall off and no new leaves are grown, it is due to light not reaching the bottom half of the plant. 

A more distributed aquarium lighting such as wide LED array or T5 array is recommended for tanks with complicated hardscape where light might not reach all the plants. A dual LED light or a T5 array provided multiple light sources for the aquarium plants, it will also increase the light intensity and will tend to reach out most of the plants in the aquarium if not all. A common example of wider spread light source is a shop light because it is designed to light larger area. However, if you decide to use it in the tank then it might give the tank yellowish color and the intensity might be below the desired requirements.  

The Right Light For Your Planted Tank:

After reading the above 3 factors, you would have an idea of what to consider before buying an aquarium light. But the question is what type of aquarium light is right for your planted tank. An aquarium with plants that require low light or low to medium light won't need high intensity light and aquatic plants with high strength light requirement won't thrive in low strength lighting. I would suggest to start with bit more research on the type of aquatic plants you have decided to put in the tank and identify the light requirement from there. Dimensions of tank also plays a pivotal role in selecting the light. A larger tank might require multiple light source to cover most of the tank. For beginners, i would suggest choosing plants with low light requirement such as ferns, mosses, cryptocoryne and anubias etc., and buy a cheap and cost effective aquarium light. And after getting bit of exposure to planted tanks then go ahead with medium to high maintenance plants.

How To Calculate Lumen/Wattage For Planted Tank:

After identifying the plants and right aquarium light, it is time to determine how many lumen or wattage will be needed for an aquarium if PAR table is not provided by manufacturer. If you want to use LED lights in the planted aquarium then for a low light planted tank, every litre of water would need 15 lumen of lighting. For a medium light tank, every litre of water would need 30 lumen and 60 lumen per litre would be required by high light tank. If you want to buy fluorescent lighting for planted aquarium then for a low light tank, every litre of water would need 0.25 watts of light. For a medium light tank, every litre of water would need 0.5 watts of light and 1 watt per litre would be required by high light tank.
  • Low light tank: 0.25 watts per litre corresponds to 15 lumen per litre
  • Medium light tank: 0.5 watts per litre corresponds to 30 lumen per litre
  • High light tank: 1 watt per litre corresponds to 60 lumen per litre

I hope you have found this article helpful and have identified the type of light suitable for your planted aquarium. Please drop a line in the comment section below and also check out my other articles on aquatic plants. I have also uploaded videos on setting up planted tanks, trimming and propagating plants; visit my youtube page for more information.

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