As an extra bulb, but not instead of, if that is the only bulb.
http://www.plantedtank.net/forums/showthread.php?t=184368
http://www.plantedtank.net/forums/showthread.php?t=594650
Funny how two charts have slightly different results. These each have a plant light absorbing range on them.
A 6700K AND a 420 or 460 would be a good combo as would a10,000K AND a 420/460.