Here is a quick video on Par levels for 250w 400w and Led. perhaps the position of the sensor was not placed properly but if you view other videos the same results come up
http://www.youtube.com/watch?v=ZVCUr...t=HL1396478548
From coral and reef 2014 "Riddle (2007) refers to a most interesting experiment with staghorn corals Arcopora austera that was exposed to different light intensities. In values 100 to 350 PAR (umol/m/sec) the corals turned brown from about 350 to 800 PAR the corals turned bright mauve. When the UV- protective filter of the metal halide Lamp was removed at 300 PAR the coral shifted from brown to bright green.
You will need a lot of halides Xenon