I have toyed with the idea of adding my 400 watt back and I did. I have one 400 watt 20K radium in the center and the corals are already responding to it. One that had a brown base last night when I added it has turned purple. At the moment it is flanked by 2-250 watt Iwasakis but I have a set of 10K bulbs on the way. The new blue line 10K. Should be interesting to see how the corals respond to the spectrum change.

MROK