For no real reason, the few times I've added new dry rock, I divert my daily water changes into a bucket with the rocks. It'll fill over the course of a few days, I'll dump it out (but leaving enough to keep the rocks submerged) and let it refill. Continue that until I get annoyed with the extra work and then toss them in the tank.
It's dry, so I'm not worried about a cycle, but people warn about spiking phosphate, so I try to remove some of that first.
It's dry, so I'm not worried about a cycle, but people warn about spiking phosphate, so I try to remove some of that first.

