Too Blue for You: Aquarium and other High Kelvin LightsPatrick R. Thrush © 1999
Is there too much of a good thing in lighting? It may seem so when looking at some of the top Color Rendition Index (CRI) and aquarium lamps that are available on the market. Like almost everything else, to achieve one effect, another must be sacrificed. This is especially true in lighting.
The concept of CRI is fairly simple. The number 100 has been established to represent how sunlight renders colors at high noon on a midsummers day. There is another factor to be considered, also. This is called Color Temperature. Rating color temperature is a system that was developed in the days of incandescent, or bulb lighting. In a light bulb, the hotter the filament, the whiter the resulting light appears. To rate this, scientists actually measured the temperature of the filament in a unit of measurement termed Kelvin (or K). In most cases 1 degree Kelvin is equal to 1 degree Centigrade.
While a fluorescent lamp never operates this hot, the same scale of “whiteness” that applies to the tungsten bulb can be used to qualify “whiteness” of fluorescent devices, or that for that matter, any source of light including daylight. Generally, the light in the sky on that same midsummers day which results in a CRI of 100 also has a Color Temperature of 5000K. So if a tube were able to mimic sunlight perfectly, it would be rated a CRI 100/5000K. Is there such a lamp? The answer to that is no, as today’s technology does not yet allow phosphor mixes to enable this output.
If we were talking about sunlight, a high color temperature in the 6000K range would be referred to as “northern sky”, owing to the amount of blue present in natural, upper atmosphere. The same principle applies to fluorescent lamps. The higher the Kelvin, the more blue the light. The sacrifice? Less red output also. So, one may ask, what difference does it make if the light has a CRI 98 at 6800K? More is better, right? The answer to this lies in the use a lamp is put to.
Aquarium lamps have long had a series called Actinic. Actinic means blue. Water naturally absorbs the shorter wavelengths of light quicker than middle and long waves, like red. So to penetrate a more equally balanced light deeper into the water, these tubes concentrate their energy into the blue. This makes for a more natural coloration of underwater objects. But most birds do not live under water, or fly miles high in the sky. Their perceptions and metabolism are balanced for living within the 100/5000K framework.
It has been long known that the application of monochromatic red light increases egg yield in poultry operations. It is also a fact that the application of monochromatic red reduces such behaviors as toe picking and feather plucking in game birds. Provision of this spectral range has typically come from the use of incandescent light which loads most of its energy into the infrared and red spectrum. Application of flourescent lighting which is deficient in red spectrum therefore can create multiple problems.
When Dr. John Ott began his research into lighting, he noticed that the application of blue monochromatic light affected the sex ratios of many animals. Subjects exposed to monochromatic blue sources resulted in higher female birth counts. This experiment has been replicated many times. Overloading of the blue spectrum produces primarily female offspring. While this may not seem bad, breeders realize that the males of the species are often the most prized, for their plumage is more distinct. A secondary discovery is that loading of the blue can adversely affect and shorten cell life.
The lack of balanced illumination in the blue has been demonstrated to cause weakness and loss of endurance, decreased resistance to disease, and lethargic behavior. Too much can cause excitement and agitation, and possible overstimulation of the endocrine system. Now, understanding is given as to why blue loaded fluorescent lamps are not particularly appropriate become clear.
Without a balanced source of light, the oculo-endocrine (light to pituitary and pineal gland) cycle is affected. This affects every aspect of a bird’s life. Skewed lighting can result in agitation, picking behaviors, weakness, breeding problems, metabolic disorders. All because the source of light is lacking in the proper ratios of blue and red. There is great indication that this imbalance may negatively affect the longevity of captive animals.
It is for these reasons that high color temperature and aquarium lamps are not appropriate for avicultural use. While a CRI 98/6800K may be the most enjoyable and healthful artificial light source for humans, the nature of this light makes them a poor choice for birds.
Copyright 1999 by Patrick Thrush