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It’s more than light,
because it’s

more than an aquarium

Philips CoralCare LED fixture

 

The unique features of CoralCare are:


• Wide spectral range - optimized for coral growth and natural reef appearance
• Perfect light balance - unique homogeneous light distribution and color mixing solution

• Low energy consumption thanks to highly efficient LEDs
• Easy to control - By intelligently combining various LEDs with different wavelengths, we have simplified the set-up of the lighting controller for the user. As a result, the user only needs to select the desired color point and intensity, without having to worry about the optimal light quality for coral growth and beautification.
• Low maintenance - long-life robust design and materials
• Easy to install - driver integrated in fixture, hanging kit included, and computer interface
 

The impact of light on coral growth


Quoted from report of Tim Wijgerde: “Proper lighting is one of the key aspects when maintaining a marine aquarium with corals and reef fishes.


First, light is essential to the growth of reef-building corals. These corals are host to symbiotic dinoflagellates known as zooxanthellae, which use light energy for photosynthesis, a biochemical process in which carbon dioxide (CO2) is converted to organic compounds such as glycerol, carbohydrates, fatty acids and amino acids. These compounds are in part translocated to the tissues of the host coral, which uses these for growth and metabolism (Muscatine et al. 1981; Muscatine 1990;


Furla et al. 2005).
When regarding light for aquaria, three factors are important; light intensity (irradiance), spectral distribution and light distribution.

 

In terms of spectrum, sufficient blue radiation is required to evoke healthy zooxanthellae and coral growth, and chlorophyll synthesis (Kinzie et al. 1984, 1987; Wang et al. 2008; Wijgerde et al. 2014).

 

In addition, to properly visualise the colours of all aquarium life, all wavelengths must be present in a given spectrum. This means that the “ideal” light spectrum for the average marine aquarium is continuous, with a blue peak to create a natural effect. This is comparable to a seawater depth of approximately 10 meters, where all colours are still found, but with decreased presence of red and orange. This is due to the fact that seawater selectively attenuates sunlight, with light of longer wavelengths being filtered more effectively (Mass et al. 2010)”.

 

As well as ensuring these primary spectral requirements, Philips Lighting has opted to improve the spectral content in order to deliver even better color rendering, maximized photosynthetically active radiation for the corals and enhanced phosphorus reflectivity.

CoralCare LED engine


The CoralCare LED engine is designed to create an optimal balance between coral growth and natural reef appearance. The design is based on various publications, our own knowledge of lighting design and scientific studies carried out with the University of Wageningen and Coral Publications.

 

Philips expertise, extensive user tests and spectrum simulation tools were used to find this balance between appearance (reefers’ color perception) and growth (ensuring coral health and good colorization).

 

With the help of the ‘light organ’ we are able to simulate any given spectrum in a contained box. The light can be tweaked and tuned in discrete wavelength steps of 5 nanometers to simulate the ideal spectrum.

Tweaking of light
aquarium light spectrum
aquarium light spectrum
aquarium light spectrum

By smartly splitting the formula into two independently controllable channels, it is possible for the end-user to adapt the color point without having to worry about setting incorrect spectral content. Our studies have shown that certain spectral settings negatively influence coral growth and could potentially lead to coral mortality.

Short-wavelength blue (400-450nm)


Many corals contain fluorescent chromo proteins and emit vivid colors if the correct light is applied. Most coral phosphors react to wavelengths of between 400 and 500 nm and emit wavelengths in a more visible area for our eyes (500-700 nm). During the evening a fully saturated blue color point can be selected to give maximum coral fluorescence. Normally this fluorescence effect is attenuated by the presence of the blue color.

 

The CoralCare light formula uses short-wavelength blue LEDs. These LEDs are much more expensive than other LEDs (factor 5x) but deliver significant benefits in terms of color, growth and appearance. If we look at the sensitivity curve of our eye and the photosensitive curve of a coral, we find that they do not correspond. A coral benefits most from the bluish wavelength, an area to which our eyes are less sensitive.

To clarify: the human eye perceives royal blue light (455 nm) to be three times brighter than short-wavelength light but coral perceives very little difference in brightness between the two. By using high-power short-wavelength blue light, we can achieve the same level of growth but without a fully saturated blue color point. This enables better color rendering of the corals, both in daylight settings and in particular in evening settings, when the coral’s fluorescence is primordial.

Fluorescence of corals
Fluorescence of corals

CoralCare LED spread analysis

The CoralCare LED fixture uses 104 high-power LEDs and 5 different wavelength sets. Due to the combination of 6 LED types, the spread of flux and color point could affect lamp-to-lamp color consistency. A detailed spread analysis was carried out to define the corner points of the total spread and the potential need for LED binning. A custom binning scheme serves to make sure the lamp-to-lamp color consistency stays within 6 SDCM (a standardized color deviation parameter). This means that any difference in color point in practice is more or less indiscernible to the human eye, enabling a wider spread of color wavelengths to be used (as long as the average color point stays within the 6 SDCM target).