Då har jag fått fel information från den källan som jag läste detta. Om det är så som arcadia säger så bevisar det ju ännu mer att vi bör ha mer av det röda spektrat i våra ljuskällor än vad vi har idag även om våglängder mellan 420-460 är det viktigaste för photosyntesen. Hittade lite bra info om ljus Light is perhaps one of the most interesting physical entities known. It is the only entity that exhibits both wave and particle properties. I haven't kept up with quantum physics, so this may have changed. Light is composed of particles called photons (I'm not talking about torpedoes), but it can be measured in wavelength. Wavelength is associated with color. The human eye can see only a small portion of the light spectrum. This range os 400nm to 700nm (nm stands for nanometers). Red is 700nm and violet is 400nm. In reef aquaria when discussing wavelength, we are typically only concerned with the violet spectrum. The violet spectrum is important because coral photosynthesis occurs in 420 to 460nm. Corals evolved to use this wavelength because as light penetrates water the other wavelength get quickly absorbed. The violet wavelength penetrates deepest. Shorter wavelength have more energy. So when you are searching for bulbs look for one with a good amount of intensity in the 400nm to 460nm if a graph is available. When we refer to actinic bulbs, we are refering to bulbs that produce light at around 450nm. So although actinic supplementation is mentioned for good color, actinic supplementation is also aiding coral photosynthesis PAR stands for Photosyntheically Adaptive Radition this is a measure often associated with metal halide bulbs. PAR is the measure of light intensity in the 400nm to 700nm range. The higher the PAR, the greater the amount of energy available for photosyntheis (coral growth). It stands without reason that one should choose a bulb with the highest PAR that is pleasing to the viewer. Pleasing to the eye is usually a function of the color temperature of a bulb or its Kelvin (K). I found this excellentdefinition on Answers.com. The measurement of color expressed in Kelvin (K). The reason this measurement is called a "temperature" is because it was derived from a theoretical object called a "black body radiator." When the radiator is heated, it changes from black to red to yellow to white to blue. The lower the Kelvin rating, the "warmer" or more yellow the light. The higher the rating, the "cooler" or more blue the light. In the aquaria industry, we encounter bulbs that range from 6500K to 20,000K. This is often abbreviated as 20K. What we typically find is that 6500K is yellow, 10,000K (10K) is white, 14,000 (14K) has a slight blue tinge, and 20,000K (20K) is quite blue. The labels that manufacturers place on their bulbs should only be used as a guideline. It is best to see the bulbs in person. Generally speaking, the higher the Kelvin, the more the corals will flouresce. The lower the Kelvin, the faster the corals will grow. Typically, the higher the Kelvin the lower the PAR. As hobbyists, reefers are always trying to find that happy medium of growth versus color.