Testing the Philips Coral Care LED's claims - Are they realistic?
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Tim Wijgerde
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Hi everyone,
My name is Tim Wijgerde, the marine biologist who led the performance study of the Philips CoralCare unit. First of all, thank you for this critical and honest discussion of the CoralCare unit. I always welcome skepticism and criticism, as long as people keep an open mind, and it seems like we have that healthy combination on this forum.
When we designed this study, we knew that several pitfalls and caveats would always exist, unless you spend several years testing out many combinations of light intensity, spectral qualities and countless coral species and genotypes. The amount of research you can do on the topic of light alone is virtually endless.
Having said that, let me explain why we used the T5 and LED setup here. As each reefer has his or her own preference in terms of applied light spectrum and perceived colour point, it was challenging to choose between the many types of available T5 bulbs, and as a result, the LED colour point. We opted for the ATI Aquablue Spezial 12,000 Kelvin bulbs since I have lots of experience with them. At Wageningen University (The Netherlands), I studied coral biology for several years (feeding rates, skeletal growth, photosynthesis, respiration, etc.), using these bulbs in ATI power modules. Although the colour point generated by these bulbs will strike many reefers as too white (or boring), it is a good, quite balanced spectrum which results in good coral growth (any photosynthetic coral grows well under these lights, provided irradiance is high enough). As I have lots of coral growth data using these T5 bulbs, it made sense to use them as a baseline for comparison with the CoralCare LED unit.
In terms of irradiance (light intensity as PAR, photosynthetically active radiation, ~400-700 nm wavelength range), we chose a medium to high value (560 µmol photons m-2 s-1), comparable to a coral reef at about 10 meters depth at noon (with clear skies). This irradiance results in fast coral growth and attractive coral pigmentation (high light intensity results in lower zooxanthellae density and/or less chlorophyll production by said zoox, depending on species, preventing a brownish appearance, and at the same time, it stimulates the production of colourful fluorescent and non-fluorescent chromoproteins by the coral).
In the comment above, rockskimmerflow suggests that a PAR of 560 µmol photons m-2 s-1 results in photoinhibition, possibly stressing the corals too much. It is indeed true that such a PAR value results in photoinhibition, which is a decrease in photosynthetic efficiency caused by light (or heat) damage to the PSII reaction centres in the zooxanthellae (which are responsible for photosynthesis, i.e. the generation of chemical energy from light energy). However, we also know that corals can perfectly cope with it, in nature as well as in aquaria, as long as 1) the corals receive a dark period for at least several hours, allowing the zoox to repair their PSII reaction centers (like a pit stop during car races) and 2) there is sufficient water flow around the corals, allowing them to dissipate the excess oxygen produced during photosynthesis, thereby preventing physiological stress. Of course, we made sure our test corals received a dark period (12 hours) and were exposed to good water flow. In fact, I am now growing a few corals in a small aquarium at 1200 µmol photons m-2 s-1, without problems J. Of course, corals have to be acclimated to such a high light intensity, which is similar to the irradiance on a coral reef at a depth of about 2,5 meters at noon (clear skies). Growing corals at such a high irradiance is not very efficient, production-wise, but it can be done and results in attractive colouration. To be honest, the LED spots in my 30 liter aquarium are responsible for this very high level at several spots, so it wasn’t really my choice a priori.
In terms of rotating the corals, although I understand this is not realistic for setups where the corals are permanently glued at a fixed position, it is important to a good coral study. If you do not rotate your corals within a treatment group, you risk exposing your corals to small variations in light field as well as water flow patterns. This can inflate the error rate (standard deviation) within groups in terms of growth rate, making it harder to obtain statistically meaningful results from the data.
To summarize, corals could care less what the light source is, T5, metal halide/HQI, LED or the sun, since a photon is a photon. However, corals do care about 1) the frequency of the photons (spectral quality), 2) the density and photoperiod of the photons (light intensity and day length) and 3) a proper dispersion of photons, with larger colonies ideally being illuminated all around to reduce self-shading at the base of the colony. Our basic study showed that with the CoralCare, you can grow corals just as well as compared to T5, with the added advantage of 30% higher wall plug efficiency (or 7.3% percentage point, the absolute/arithmetic difference between two percentages) and long-life span of the CoralCare unit. I can understand reefers would like to see studies where both light sources are set to a more blue colour point, with other coral species, etc., but there is a limit to what you can test within the boundaries of a commercial enterprise. I personally commend Philips for the fact that they don’t slap unfounded claims on a pretty box, but that they instead actually do extensive testing before they sell any product.
I understand a given product is not for everyone, and so too the CoralCare unit may not appeal to everyone, but I still hope this product gets a fair chance. It really is a good light source, notwithstanding the quality of other, competitive products. At Wageningen University, the coral lab is currently being refurbished with twenty CoralCare units, as they save time and money since no bulbs need to be replaced every four months (T5 bulbs quickly degenerate, with a loss of blue light and resulting shift in spectral quality and irradiance. This is problematic for scientific studies).
I hope that my contribution has provided some insight into the choices we made for our experiment. Thanks for reading my post, stay frosty and happy reefing to all!!!
Cheers,
Tim
Tim Wijgerde
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P.S.
Some reefers also want to know how the CoralCare unit compares to a single T5 luminaire. To give you an idea, one CoralCare unit (190 Watts) at full power results in a similar light field compared to a 10 x 24W T5 ATI power module (240 Watts). It's a bit apples and oranges, but it gets reasonably close.
Some reefers also want to know how the CoralCare unit compares to a single T5 luminaire. To give you an idea, one CoralCare unit (190 Watts) at full power results in a similar light field compared to a 10 x 24W T5 ATI power module (240 Watts). It's a bit apples and oranges, but it gets reasonably close.
Tim it's a good start in the right direction. Using a already available fixture helped get the light into production. Reducing the direct light of LED's and the resultant shading and hot spots. Is an area up until now that LED sellers have not addressed.
I think BRS did a great job reviewing this new light.
http://www.bulkreefsupply.com/video...ps-coral-care-leds-claims-are-they-realistic/
http://www.bulkreefsupply.com/video...ps-coral-care-leds-claims-are-they-realistic/
Only for those who can afford the $1200 starting price.
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I got one. It's currently sitting waiting to come out of customs in San Francisco. I'm thinking Wed or so should be at my door.
Ohh and it was less than an XR30 G4 Pro even counting being shipped halfway across the world.
swk
Well-Known Member
Absolutely. If a tank is worth anything, I spend very little time looking at the lights.
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