Aquarium Moon Lights Review; Is Moonlite truly Blue

Updated 11/26/11

The use of Moonlights in aquariums (Reef in particular) is one of the most misunderstood and inaccurately stated subjects that is sadly repeated by aquarium forums, websites, product manufacturers, and retailers.
The simple fact is moonlite is NOT Blue, rather this is a perception due to Rod Cone Interaction in the human eye.
See: Modeling Blue shift in Moonlit Scenes by Rod Cone Interaction

If you go outside on a purely moonlit night the surrounding appears to have a tinge of blue. This phenomenon often referred to as ‘Blue Shift’ is a perceptual illusion. Moon light itself is not blue; moonlight is simply full spectrum sunlight reflected off the grayish
surface of the moon. It is hard to observe blue shift in cities due to many artificial
sources of light, however it is a commonly observed phenomenon in places with low ambient light.
The blue shift is sometimes attributed to the spectral response of rods. Although rods are nominally color blind, they do not respond equally to all colors: Rods are more sensitive to blue-green photons and less sensitive to red photons. You can see this in your moonlit rose. By day, the red flower dominates the green leaves. At night, the situation is reversed. The green leaves are more vivid than the red flower.

Correct Application of Moon Light for Aquarium Use

Since even a full moon only reflects .2 lux of sunlight which is only about 1/400,000 to 500,000 the brightness of the sun, the main implication is the amount of light, as some studies suggest that plants and photosynthetic algae (such as the zooxanthellae that light sensitive corals, clams, nudibranchs and similar rely upon) are effected by bright full moon phases. So the implication is not how blue the light is, rather than how bright the “moonlight” is (moonlight is slightly higher at Tropical latitudes and even up to 1 lux at high altitudes at the equator, which of coarse there are no reefs on mountain tops in Nepal, except maybe according to Yahoo Answers LOL).
As well the Lunar phase or cycle is also extremely important as well in this equation, as coral reproduction/propagation spawns are 3-7 days following the first 2 Full moons in late spring and early summer (as found in the Great Barrier reef of Australia).

What an aquarium keeper needs to be concerned about if truly attempting to replicate Moonlite for his Reef aquarium is not the color, but the precise amount of light in a constantly dimming (from full to new moon) or increasing amount of moonlight (from new moon to full moon). This also must be in a lunar cycle which is 29.5 days (the Lunar Phase is 27.3 days).
See this website for more about the lunar cycle: Moon Calculator


Since timers are set up on a solar calendar, this is not possible with most of the equipment currently available in the aquarium hobby. This would take someone with precise measurements entered into a computer program to then plug ones aquarium Lights into these.
The other problem is the ability to dim and un-dim the moonlights according to the phases of the Moon; which would require a dimming, controller that recognizes these phase according to the lunar calendar to perform this function (your computer likely cannot perform this function.

For these functions (when available), LED Aquarium Lights are clearly the best choice and these should be full spectrum or at least a full spectrum mix such as the AquaRay Reef White.

Even without the ability to phase a moonlight phase via a lunar calendar, with the aid of a controller (such as TMC Standard and Multi-Controller with Storm Feature), an aquarium keeper can run their aquarium LED lights anywhere from 100% to 0%. As well these percentages can be slowly ramped up and down to create varying amounts of sun light.
As an example, for a Reef Tank; I would run the LED lights at 100% for 8 hours per day with 2 hour ramp up and 2 hour ramp down at the beginning and end of the day. Finally generally only 1% is required for moonlight (although you could manually vary this for more accurate moon light effects).

For those that insist on Blue Moon Lights and think they are providing an essential ingredient for a healthy reef aquarium, they are fooling themselves and only providing at best “cool” night lights for their aquarium.

For much more about Aquarium Lighting, including a discussion of Moon Lights, please visit this web page:
Aquarium Lighting; Facts & Information


Further Resources:
*Strange Moonlight
*Interference of moonlight with the photoperiodic measurement of time by plants
*UV Bulbs