Wow, glad I ran into this thread. I thought it was just me who had this stuff. I had been reading every thread about "red algae" I could find, but up until this one it always seemed end up being cyano or something. By the way, my tank is a BB as well, and all my rock was cooked minimum of about 3 months. I had a similar observation with this in my previous (and seriously unhealthy) tank. If I had a frag that was not doing well, this stuff would just grow right up it.
I currently have about 20 astreas, and 10 ceriths, and just added an emerald crab. Haven't noticed a real difference yet, but we'll see.