ADVANCES IN REEF LIGHTING ACTINIC 03 vs

ADVANCES IN REEF LIGHTING
ACTINIC 03 vs. ULTRA ACTINIC

In the early days of the reef hobby, a combination of full spectrum lighting supplemented with actinic 03 lighting (that is, lighting that ranges from ~380 nm to ~480 nm, with a major peak at ~420 nm; Fig. 1) was used to meet the spectral requirements of zooxanthellae. It was known that this alga utilized blue light, and the actinic 03 bulb provided the closest spectrum at that time. This combination of lighting generally met the requirements of zooxanthellae, and, for the most part, corals did very well under such lighting. However, with advances in lighting, the question arises as to just how adequate this lighting regime is, and is there anything better.

To answer these questions, we should look to the whole absorbance spectra of zooxanthellae (Fig. 2). As you can see, this spectra has a narrow peak at ~460 nm. When you break this down further (Fig. 2), it is noted that chlorophyll b and some carotenoid pigments peak within that range (~450 nm to ~460 nm). It is only chlorophyll a that peaks in the ~420 nm area, along with some carotenoids that peak at ~430 nm. It is also interesting to note that energy absorbed by zooxanthellae at 380 nm fluoresces in a range between 450 nm and 530 nm, and range into which chlorophyll b and some carotenoid pigments fall, and outside the major absorbance peak of chlorophyll a.

In clear reef environments, the wavelengths of maximum penetration fall between 440 nm and 490 nm. This may explain, in part, the spectral peaks of chlorophyll b and some carotenoid pigments. This is not to say that other wavelengths are not represented or utilized by zooxanthellae, just that their energy relative to the above-mentioned range is not as great, especially as one goes deeper. Looking at the spectra in Fig. 1, it can be clearly seen that there is a broad peak from 400 nm to 550 nm and a narrower peak between 650 nm and 700 nm. However, while zooxanthellae do use light within these ranges, it must be remembered that the greatest absorbance occurs within the relatively narrow range of ~450 nm to ~460 nm.

So, where does this leave the reef hobbyist? While the actinic 03 bulb is adequate to the task, is there anything better? In my opinion, yes there is.

Custom Sealife has developed a bulb which peaks at ~460 nm (with a smaller peak at ~420 nm; Fig. 3) which matches more closely the absorbance spectra of zooxanthellae. This bulb, called Ultra-actinic, has a major peak at ~460 nm, which happens to be the greatest absorbance area for zooxanthellae! This light, in my opinion, is a major step above the use of actinic 03 as it provides a more usable spectral distribution. Combined with the Custom Sealife Ultra daylight bulb, the spectrum matches very closely that of the absorbance spectra for zooxanthellae, with peaks in both the ~400 nm to ~550 nm range and the ~650 nm to ~700 nm range. In theory, then, the zooxanthellae are able to utilize a greater portion of the light hitting them than they might using an actinic 03/full spectrum bulb combination.

Practical experience has shown me, as well as a host of other hobbyists, the the use of these bulbs in combination allows for superb stony and soft coral growth and color, matching those produced by metal halide lighting of similar wattage. When compared to VHO lighting, the results are far superior.

Just as we have left behind our undergravel filters and other antiquated pieces of equipment, perhaps it is time for us to discard our actinic bulbs and our overly hot metal halide fixtures and take a giant step forward in reef lighting. I believe the use of both Ultra-Actinic and Ultra-Daylight bulbs IS that step forward.