I was looking for these answers myself this last week , perhaps these Will help
Just keep in mind how adaptable coral are . Iv read of ppl keeping ricordia under 300 MH , and iv witnessed them melt under far less .
http://www.livingreefs.com/threads/corals-and-lighting.839/">http://www.livingreefs.com/threads/corals-and-lighting.839/</a>
These seem awfully high and I don't agree completely.
This is more realistic to my systems performance
[IMG]http://answers.seneye.com/en/Aquarium_help/what_is_PAR_%3F/marine_coral_reef_PAR_levels">http://answers.seneye.com/en/Aquarium_help/what_is_PAR_%3F/marine_coral_reef_PAR_levels</a>