Wattage measures the amount of
electricity in a bulb. The higher the wattage, the brighter the
bulb. Kelvin rating measures the color and intensity of
the bulb. The higher the K, the more blue the light. The lower
the K, the more yellow. 10K is white light. 14K is bluer. And
20K is bluest. 10K (white light) is best for fastest coral
growth but not color. 20K (blue light) is best for color but not
for growth. We recommend 14K for coral growth and color.