As ziggy said the lamps will shift K, and emit more light in/towards the red spectrum overtime. Those spectrums are not easily used by coral, but are good for nuisance algaes. The lamps loose intensity as well. As far as what kind of lamps, a 10 k and an actinic (blue) make a good combo IMO. It's partly a matter of personal preference. I used VHO's and the 10 k and actinic is a good mix of blue and white/yellow(~daylight) leaning a bit on the blue side to get more pop from fish, coral colors. I can't recommend any brands, I've never purchased PC lamps.