Hi
macboat,
The simple answer to your specific question is 200 lux. According to Jokiel
et al., 1985, full moon PPFD or photosynthetic photon-flux density is 0.01 micro E / m(squared)s while midday readings showed 2,000 micro E / m(squared)s. Moonlight at full moon equals only 1/200,000th sunlight at noon.
Since I have already discussed this in some detail in another thread years ago, I will go ahead and post that same response in here for the benefit of others who may have other questions besides the very narrow one you posed.
Steve Tyree covered moonlight intensity in
an article he wrote back in 1992. He evidently covered it in even greater detail in another article in 1994 because his artificial moonlight in the aquarium charts have been copied in Fossa & Nilsen's
The Modern Coral Reef Aquarium, Volume One on pages 201 and 202. The maximum at full moon would give a reading of 200 lux incident on the surface of the corals. Most of the month it would be much less intense than that and for a third of the month it would be less than 40 lux. In fact, for eight days near new moon it would be less than 20 lux.
You can duplicate those conditions with one or more (depending on the surface area of your tank) 25w blue incandescent lamps controlled by a computer, such as Neptune Systems Aquacontroller, that dims the lamps to replicate natural moonlight intensity depending on the phase of the moon. The controller also turns the moonlight on and off in accordance with natural moonrise and moonset schedules, which means that your moonlight's photoperiod will vary each night and it will even be on during the daylight part of the time -- the new moon rises with the sun, the full moon rises with sunset.
If you don't have a computer controller for your moonlight, just check with the
Naval Observatory's handy little moonrise and moonset calculator and reset your timer every day. Oh, and you would need to have a dimmer, too, so that you could adjust the intensity based on the appropriate phase.
Maybe your local area's website gives moonrise and moonset times? San Francisco's moonrise and moonset times for today and tomorrow appear at the top of their live views page:
http://www.sfgate.com/liveviews/ It's possible to replicate natural moonlight over your aquarium without the use of a controller but it will require a considerable amount of effort. A controller that is pre-programmed makes things a lot easier.
Please be sure to follow that link to Steve Tyree's articles for detailed information on this topic.
Thanks!
P.S. -- Most of the so-called moonlights that are on the market today replicate the full moon only and often they are much brighter than the full moon. They don't replicate natural moonrise and moonset cycles and they don't adjust intensity to replicate the phases of the moon. Such lights are not moonlights, they are nightlights for the amusement of nighttime viewers. They do not replicate natural conditions that are important natural cues in the reproductive cycles of many of the animals we keep in our aquariums. More likely than not, they only add a new element of confusion to the system.
