In the marine hobby, lighting is a hotly debated subject. To quantify light, the lux unit is often used, which is the amount of lumens per square meter. Although this unit is very useful to quantify lighting equipment which is perceived by the human eye, it is of little value to the aquarium hobby or aquaculture. This is because lux and lumen are based on the green portion of the light spectrum (approximately 555 nanometers), whilst zooxanthellae, as most plants, benefit more from the red and blue portions. This is due to the fact that the photosynthetic pigments residing in zooxanthellae have the highest light absorption, and thus photosynthetic activity, when exposed to red and blue light. This principle has lead to much confusion. Light sources with little green and yellow light such as LED fixtures may seem quite dim to our eyes, while they can have a high output in the red and blue parts of the spectrum. Such a ‘weak’ light source may in fact be quite appropriate for culturing corals.
Although the human eye may not be a reliable light meter, alternatives fortunately exist. With industrial light meters, light sources can be measured accurately. A common unit of measure for light intensity is the mole or Einstein. Scientists often use the notation
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and half of what I typed just got cut off........I'll retype my thoughts later
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