Coral Coloration and How to Get The Best "Look" With Your Reef Tank Lighting - BRStv Investigates

The intense color you can achieve in a reef tank among both the fish and corals is arguably the most captivating aspect of a saltwater reef aquarium. There really is nothing in the natural world that even closely rivals a reef in terms of colors.  Even the most basic reef aquariums are painted with a rainbow of colors from fluorescent neon green to a deep magenta and everything in between. 

Naturally, reef aquarists strive to produce the best possible coloration and, for the most part, this just means keeping healthy fish and corals so they look their best. That said, lighting heavily influences the aesthetic of our reef aquariums, more specifically, how our eyes perceive the colors in our tanks.

How Does Light Effect Color?

When it comes to seeing colors, lighting is everything. When our eyes see color, we are actually seeing a reflection of specific light wavelengths reflected by color pigments. The easiest example would be the green leaves on a tree - leaves contain green pigments that reflect only the green wavelengths of light into our eyes and absorb the remaining wavelengths. A red crayon contains red pigments that reflect red wavelengths and so on. 

Without the right wavelength of light, our eyes contact perceive or "see" that color even if the pigment exists. If you put a red crayon under a light that only contains green wavelengths, it will not appear red. For the most part, it will just look some shade of green.

In our tanks, things work the same way. The corals or fish must contain the pigment and the light must contain the wavelengths in order for us to see the color. This isn't unique to reef aquariums either, freshwater aquariums are governed by the same phenomena. 

Chasing Fluorescence

What is unique to reef aquariums is the presence of fluorescent proteins which are responsible for that glowing or "blacklight" effect. Fluorescent proteins absorb high-energy blue-violet light and then remit that light at lower energy wavelengths such as green, red, yellow, or orange. Rather than a reflection from the color pigment, it's a transformation of light wavelengths by fluorescent proteins.

If you want to know which corals contain fluorescent proteins, turn off all the lights except for the blue spectrum. Any coral that is NOT blue contains fluorescent proteins.

Different fluorescent proteins will absorb this high-energy light at different wavelengths which results in different colors. For example, a peak in the violet wavelengths (420nm) might create a very neon green while a peak in the blue-indigo (480 - 500nm) wavelengths will highlight red or orange fluorescent proteins.

The Optical Illusion of Color

This fluorescence combined with the multitude of color pigments is what makes a reef aquarium so visually stunning. All of the different shades and hues of color are made possible because a vast majority of the colors we see in our aquariums are actually a blend of fluorescent proteins, color pigments, and the light spectrums illuminating them. For example, purple corals contain blue and red pigments that appear purple to our eyes. A fluorescent red protein combined with a blue pigment will appear as glowing purple. The thing is, our eyes will see this color blend differently based on the light spectrum, and the key to achieving contrast and the most impressive color pop is to provide a balanced light spectrum.

Achieving The Best Fluorescence

When you start to adjust spectrum peaks, you can see how the fluorescent colors shift in your aquarium. See the examples above with the same exact coral under full spectrum light and various high-energy spectrum peaks. Note the Forest Fire Digitata (orange) coral in the bottom right corner and how it shifts drastically between the various peaks. Check out how the tabling Acropora coral transforms from a bland cream color to an intense green with purple tips. 

A coral that looks drab under full-spectrum white light may very well look incredibly brilliant under a light spectrum containing peaks in the violet-blue wavelengths. If a light spectrum is missing a peak anywhere in this high-energy blue bland, you are not achieving the best balance of fluorescence across all of the possible fluorescent pigments. One fluorescing coral may look great, but others will not be as showy simply because of missing spectrum peaks. 

It's all about balance. A wide band with equal peaks in the violet, blue, and indigo wavelengths will produce the best balance of fluorescence in a reef aquarium. 

Using adjustable LEDs at home, you can easily experiment with the various light spectrums and see how these peaks highlight the colors in your aquarium. You may also be able to identify missing wavelength peaks which means you can achieve better color and improve your coral's health by simply providing a more balanced light spectrum. 

What We've Learned...

1. The same exact wide band of violet, blue, and indigo light spectrums corals need for photosynthesis are the same exact spectrum peaks that create the most visually stunning colors in our aquariums.  It's a win-win situation where the health of the coral and our desires for a picturesque reef are satisfied by providing the right light spectrum. 
2. Capturing your corals with a camera is best done via a top-down approach which is how we filmed everything without any color correction or boosting during editing. You may be surprised at how well you can capture the color of your tank from the top-down angle using a coral viewer or camera tube. 
3. We did not analyze true ultraviolet light because our eyes are simply not sensitive to these color spectrums; we just can't see any difference. The answer to whether or not true UV light is beneficial in our tanks lies within the biology of the coral. What role, if any, does UV light play in the health of a coral?  One caveat is the documented cases of corals changing the ratio of color pigments based on the presence of UV light. Your corals can change color based on the light spectrum.  NOTE: While many reef aquarium lights advertise "UV" LEDs in their diode spread, this is often referring to the 400-420nm violet range which is not true UV. True UVA exists at 315 - 400nm wavelengths which we cannot see with our eyes and is very rare in a reef aquarium LED. 
4. What about color pigments and white light? Most all aquarium lights contain either cool or warm white LEDs which highlight the remainder of the color pigments in your tank. The most dramatic effect we can have on color is done within the high-energy wavelength peaks and adjustments to the remaining peaks will vary based on preference. Cool white has a peak in the blue 450nm range whereas warm white is more balanced with peaks in the red-yellow-orange wavelengths; since most reef tank LEDs have plenty of 450nm blue light, warm white is the most useful in terms of producing the best coloration. 
5. There is no right answer to the perfect spectrum; every tank is different in terms of the exact corals and how they will appear best is subjective. Start with the foundation of a wide blue band to meet the biological needs of the coral and create the best possible fluorescence then intelligently adjust the remaining color peaks to highlight the corals in your tank as you see fit. 
6. Fluorescence cannot be achieved without corals that contain fluorescent proteins so it all starts with acquiring corals that "glow".  Bring a blue flashlight to the store and buy the corals that "pop" or glow because they contain fluorescent proteins. Provide the optimal light spectrum in your tank at home to achieve that same (or better) level of fluorescence you witnessed when buying the coral. 
7. Below is the blend we used to provide the best-balanced spectrum using an EcoTech Marine Radion Pro.
   1. UV - 100%
   2. Violet - 100%
   3. Royal - 33%
   4. Blue - 100%
   5. Green - 33%
   6. Red - 33%
   7. Warm White - 100%
   8. Cool White - 33%
8. What if my light is missing violet or indigo light wavelength peaks? Most all modern LEDs will contain plenty of 450nm blue wavelength peaks and in many cases at least some amount of indigo/light blue. The most common missing peak is the violet (420nm) range. If your high-energy spectrum is lacking, start with the violet range to achieve better fluorescence among purple and neon green proteins. Boosting the light blue and indigo bands will improve the rendition of red and orange fluorescing proteins. Ultimately, the ability to control all three wavelength peaks (violet, blue, and indigo) will allow you to create even peaks and achieve the best coloration.
   1. Buy new lights that are able to provide a balanced spectrum (most expensive) 
   2. Supplement with T5s (not adjustable)
   3. Supplement with LED strip lights (most flexible & likely most affordable)