Here in the US we love our 20ks. Radium, XM, Reeflux “12K”, and Helios are all popular bulbs because of their heavy blue spectrum. In actuality the kelvin ratings for these blue bulbs are marketing and only recognized within the hobby. These blue lights can do wonders for brown Acroporas and actually wash them blue, often times [...]
Here in the US we love our 20ks. Radium, XM, Reeflux “12K”, and Helios are all popular bulbs because of their heavy blue spectrum. In actuality the kelvin ratings for these blue bulbs are marketing and only recognized within the hobby. These blue lights can do wonders for brown Acroporas and actually wash them blue, often times making them appear more colorful then they actually are. The blue wavelengths can also cause florescence. However, it’s not always the best way to display corals. In fact warm temperature bulbs mixed in or alone can enhance coloration even more.
A red coral reflects red light. If a red light is focused on this coral it will appear more red as it reflects more of that red light. With spotlights being difficult to acquire in the US there are other options available such as T5s, PCs and even lower kelvin halides to provide warmer wavelengths often omitted from the popular 20K bulbs. The effects can be quite drastic as shown below by our friend Hideki’s beautiful LPS nano, dominated by Acanthastreas and Eviota Gobies. A heavy blue color temperature highlights greens and blues very well, but often loses the vivid red and pinks. In Japan these warmer colored bulbs are occasionally called “Neon” for the coloration they bring out.
A common bulb used in Japan to bring out purple, pinks and red is the RB37 or NZRB37. It is available as a straight tube T8 style or a CFL spot light with an internal ballast. Shown below are 5 of the common CFL style spots used.
We wont be seeing these anytime soon, but for the time being don’t be afraid to try new lights out. Even the CFL lights used for refugiums in the common 6.5K can provide warmer light to enhance color and provide highlights in otherwise blue dominated lighting. (Be sure to use reflectors or those with a built in flood light style PAR reflector.)
Other options available include Osram/Sylvania Pink tubes and Pink CFLs. These are not commonly carried, but if you go to a Sylvania distributor they should be able to obtain them for you. Freshwater bulbs are also generally warmer in color temperature and provide some interesting and often overlooked options. The low wattage of these bulbs makes their addition inexpensive, and their effect barely noticeable–Halides will wash out most of the warmer light, but the effect on the coral should still be seen.
At the end of the day these are for aesthetics not for growth or health, but the depth and variety that warmer lights can provide are often well worth the additional cost.
