You can place the rock in a separate tank or a large rubbermaid container with salt water, a heater and some sort of powerhead. It can take a few weeks to get all the die off to happen and cycle. If you were to put in that rock now you most likely would get a huge ammonia spike and possibly lose your fish. :-(
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.