Piggy,
I'm going to let the 210 cycle with 100lbs of live rock first.Transfer the 120lbs of live rock and the sand from the 75 to the 210.Its may start another mini-cycle.Keep my fish and corals in 2 10g, QT for how ever long it takes to return to normal,add fish and corals over a period of a week or two.I probably being overly cautious but all well.