Radiums are best run on pulse start magnetic ballasts. They also fire up on electronic ballasts but the spectral balance shifts towards blue because they are underpowered. Except for 400w Radiums all the other wattages draw more power than rated. The 150w Radium burns at 228w on a m81 ballast! I want to run Radiums on my tank so did a bunch of research on other boards to get the info.
Check this out: http://www.manhattanreefs.com/lighting