Not all 10,000K lights are created equal. His light(50/50) is a 'single' light bulb that is a mixture of half actinic/half 10,000k...not two seperate bulbs. I agree, straight actinic blues will do nothing for plants, but 50/50s are fine, especially when paired with a 6700k bulb. Plus we're talking about PCs here, plenty of light output.
As far as the actinics causing algae blooms, it should only be a problem in tanks with high DOC or excessive nutrients in the water column. It has something to do with blue and UV light reducing or freeing up normally bound-iron(iron precipitates, or iron bound with doc), making it readily available to algae. This is called photo-reduction of iron.
Personally, however, I recommend getting some GE Aqua-Rays Freshwater/Saltwater 9325K bulbs and pair them with the 6700K ones, as this generally gives very good results with plant growth and looks great, as well.
