Many experts recommend selecting lighting with a bulb Kelvin color between 6,500K and 10,000K because it promotes optimum coral growth. These color temperatures represent the daylight spectrum and can range from a yellow appearance to a crisp white. Although many aquarists get good color growth, oftentimes their aquarium did not look very appealing. In fact, most people like an aquarium with a slight blue tint.
Actinic Aquarium Bulbs
The invention of blue actinic bulbs, which create a similar effect as a black light, causes some corals to fluoresce. The most common colors are green, red and yellow. As more advanced bulbs were developed, scientists discovered that bulbs producing light between 420nm and 460nm created the most fluorescent in corals and that is why these are the most commonly available bulbs today. These bulbs may also be labeled 20,000K, which refers to the blue color spectrum on the Kelvin scale.
The previous downside to these bulbs is they used to lack intensity, so they did not promote coral growth. As a result, many hobbyists used a combination of daylight and actinic bulbs to create a coral reef aquarium that had good coral growth, an appealing water color and caused fluorescence in the invertebrates.
Aquarium Light Bulb Fixtures
With new modern T5 and LED lighting technology, the actinic light bulbs are nearly as intense as the daylight bulbs. In fact, some of the bulbs are so bright that the newest fixtures have built in light timers to dial back the intensity of the light. Some LED fixtures even let you control the exact color of the bulb and then can be changed throughout the day to simulate sunrise and sunset. So to answer the question, what bulb color should I select for my aquarium? You should select the color that is most appealing to your eyes, as the intensities of actinic bulbs nearly match those of fluorescent daylight bulbs.