Quoting: "Lux on a tropical reef has been measured to be between 110,000 and 120,000 at the surface and 20,000 to 25,000 one meter below the surface."
This is equivalent to a 75% drop per 3 feet. If we assume a linear reduction this means 25% drop per 12" (couldn't find equation for drop off) or 2% per inch. My tank therefor has the following characteristics:
Tank Height: 27"
Surface: LUX: 25,000
Highest Rocks: LUX: 22,000 (surface * .88)
Middle (where My archs are and most rock structures are: LUX: 18,500 (surface * .74)
Bottom: LUX: 13,500 (surace * .54)
From a LUX perspective; this would mean my tank replicates conditions beginning at approximately 3 feet of depth. A typical shallow tropical reef exists upwards of 150 feet depth in the ocean. My calculations are obviously not able to be correct because light is required to produce corals and at 100 feet; this would be no light. therefor the initial surface penetration is likely a very large drop while pushing through the medium is a lower drop.