[jcltok]

I have always wondered why hobbyists focus on watts. The real question is whether the coral is getting enough light - lumen. At sea level, the sun provides about 2650 lumen per square foot.

The other is PAR - you need 1800 microMol/m2/sec. Any quantum meter will show you. You have to be careful about lights that achieve high PAR by boosting the violet/blue spectrum at the expense of the rest. A balanced spectrum is needed.

You can define better or worse balanced spectrum by looking at the CCT. The CCT of many high Kelvin MH are around .26 X .26 which is too far away from a balanced spectrum. Certain deeply growing corals will do fine, but it makes it tougher to raise a larger range of coral.

A CCT of about .31 X.31 is more appropriate when you have corals that normally grow in a wider range of depths.