salwater fish do not need 12,000k bulbs.
FO and FOWLR tanks do perfectly fine with standard output bulbs at 6500k or less
lower kelvin temp = more yellow
higher kelvin temp = more blue
for corals higher K will help color and lower K will help growth
dont go under 10,000k for reef tanks
but seriously... look at the sticky's and use the search function this has been covered 1,000's of times