Years ago (in the dark ages, pun intended) we believed intense light was a prerequisite for success with corals, especially SPS. At one point, we actually tested a Fusion sulfur lamp that produced so much light that it maxed out the PAR (measured up to 20,000 micromole/m2/sec.) We know now that corals can grow quite well in low light (if other parameters are in order.) So, what's your lowest PAR that keeps a coral alive (we'll keep growth rates out of the equation for now.) It would be great if you want to mention the lamp type/spectral quality.