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Reef Tank Lighting Spectrum

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Last updated on November 17th, 2023


Reef Tank Lighting Spectrum

What is Reef Tank Lighting Spectrum

Reef Tank Lighting Spectrum is the combination of light colors used when lighting your aquarium. While most of us use blue light to make the coral's color pop, there is actually more information becoming available for which reef tank light colors are better, or even needed, for coral growth and health!

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The Blue vs White Light Grows Coral Best Debate

Before I talk to you more about the different reef tank color spectrums, I want to address the long-lasting debate where you hear "blue light grows coral faster". Then another expert will talk about most coral living in an area with white light, not blue. In addition, they may have a great looking reef running white lights.

So Which One Is Right?

The answer is actually both. While I will get more in-depth about reef lighting color spectrums shortly, what you need to know is that white light is actually a combination of all lighting spectrums. That is shown below by shining a white light into a glass prism. It's more than just a band's album cover, it's actually science! White light contains all of the colors, which, as you'll see, contains blue light as well.

White Light in Glass Prism - Showing Multiple Colors

Science Behind Coral Growth and Reef Tank Light Spectrum

Buckle up and get ready, this one might get a little complicated. But I will do my best to simplify it, not only for you, but for myself as well.

Since this can be a complex topic, I am going to add this video from BRS right away because they do a good job explaining it. But I will reiterate the important details here to save you time.

Bulk Reef Supply - PUR - Quality of Light Spectrum

PUR vs PAR - What's the difference?

The common way that we measure reef tank light is with PAR, or Photosynthetically Active Radiation. PAR measures the total amount, or intensity, of light. This could be any light color, white, red, blue, anything. PAR is simply the strength of the light.

With more research, we find that coral utilizes specific coral wavelengths, or colors, to grow. I'll get more into this shortly. This is where PUR comes in the picture.

PUR is Photosynthetically Usable Radiation. This is the amount of light (similar to PAR) of the color spectrum, or wavelength, that coral uses to grow. So instead of the total amount of light, it's the amount of light with specific color. Unfortunately, since every coral is going to be different, there isn't a meter to check PAR. You would need to measure the color spectrum with a spectrometer in order to find this yourself.

What Color Light is Best For Growing Coral

Getting a bit deeper in the science, the Zooxanthellae within the coral absorbs light and provides energy to the coral through photosynthesis. The Zooxanthellae uses chlorophyll a, chlorophyll c, perdinin, and diadinoxanthin to absorb the light. Don't get too hung up of the biological detail, I will simplify some of this shortly.

Chlorophyll A for Coral Growth

Chlorophyll a gets it's energy from violet-blue and orange-red light. Chlorophyll A gathers most of it's energy from uv and blue lights, specifically around 360nm to 440nm wavelength, and then reds from 650nm to 670nm. There is still debate around the use of red light for coral growth, so I would caution going all in right away, but this could go either way yet.

Chlorophyll A Usable Light Spectrum

Chlorophyll C for Coral Growth

The role of Chlorophyll C (For coral, it should seem specifically Chlorophyll C2) is to gether the energy from different color spectrums and pass the energy back to Chlorophyll A. Chlorophyll C gets it's energy from slightly warmer lights in the blue-green color range when compared to Chlorophyll A. Chlorophyll C get's its energy from 447nm - 452nm

Chlorophyll C2 Usable Light Spectrum

Peridinin for Coral Growth

The role of Peridinin, like chlorophyll c, is to gether the energy from different color spectrums and pass the energy back to Chlorophyll A. Peridinin gets it's energy from a much wider color range when compared to Chlorophyll A and Chlorophyll C. Peridinin get's its energy from the 350nm to 500nm range. This essentially adds the 470nm to 550nm range to what the Chlorophyll absorbs.

Peridinin Usable Light Spectrum

Usable Color Spectrum for Coral Growth

When you overlay these spectrums (image below - sorry for the poor quality) you will notice that the majority of the coral energy comes from around the 380nm to 500nm range. Recognizing that most of the ranges simply pass energy back to chlorophyll a, I would also suggest adding the focus to that chlorophyll a range of around 360nm to 440nm and adding the rest as the secondary focus.

Overlay of Usable Light Spectrum for Coral

Summary of Usable Color Spectrum

Summarizing the Chlorophyll and Peridinin light absorption, Bulk Reef Supply created what they are calling the Biology Band. This is the range of light that the Chlorophyll and Peridinin absorb and use to provide energy and grow coral. This is the range of color spectrums that you would ideally focus on for coral growth.

Biology Band of Usable Light Spectrum for Coral

Which Reef Tank Light has the Best Color Spectrum

While I'm sure we would all like to start measuring light and get that "secret formula" to coral growth lights, these spectrometers are very expensive. That said, Bulk Reef Supply did a good summary of the largest name reef tank lights. Start there, but outside of this video, most reef tank light manufacturers have these spectrums on their websites as well!

Outside of the Bulk Reef Supply Video, I will note that nearly every reef light was able to provide the spectrum desired for Chlorophyll C2, but almost NONE of them hit the mark for Chlorophyll A. But BRS missed a CRITICAL supplemental light. The Orphek OR3 UV Violet Plus. This bar is designed SPECIFICALLY for the Chlorophyll A range in coral, with spectrums from about 390nm to 447nm! The perfect addition to any other reef tank light!

Additionally, I will note that the Orphek OR3 Blue Sky is designed to fill the need for Chlorophyll C2 and a little bit of Chlorophyll A. Finally the Orphek OR3 Blue Plus has a combination of both of these! Making a combination of Orphek OR3 bars a PERFECT solution to all coral growth needs.

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I know this article had a lot of deep information. The main takeaway is that coral utilizes a specific range of light for growth. If you focus on this wavelength of 380nm to 500nm, you can actually use less PAR and grow coral faster. While you may prefer to ramp up specific colors to make your coral look better, and that is perfectly fine, this is how you can focus on coral growth.

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About the Author

Reef Stable Founder John Krenzer

John is a Software Engineer with a passion for saltwater aquariums, as well as the founder and president of Reef Stable. He started in the aquarium hobby as a child with a 20 gallon freshwater aquarium. His interest in aquarium life grew and in 2008, John set up his first saltwater aquarium.

Today, John maintains an over 300 gallon reef tank system, consisting of a 120g reef and a 210g reef. These large tanks are contained within the same system, sharing a sump as a means to reduce total maintenance and increase total water volume.

John writes articles for the blog as a means to learn about more reef aquarium topics. These articles act as a reference for the readers as well as himself. John updates these articles frequently to provide additional information or make corrections as new information becomes available.

If you would like to request an article, tank tour article, or to collaborate, let me know via the Contact Me Page!

About Reef Stable

Reef Stable was initially founded in 2019 as a reef tank parameter log to fill a need. Reef Stable quickly grew, becoming a location to solve all of your reef tank problems as well as a place to learn.

Reef Stable now provides a Reef Blog, Reef Aquarium Guides, Coral Care Guides, Identification and Solutions for Pests and Algae, and Reef Dosing Calculators, in addition to the original Reef Parameter Log.

Reef Stable continues to grow, striving to provide a single location for all your reef tank needs!

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