Please don’t kill everything, this will cause you to go through another cycle. The best way to ‘clean’ used live rock is to allow the rocks to sit in saltwater with a powerhead to circulate. This allows the good bacteria to stay in the rock but should isolate/kill anything else. The dark will kill corals and any hitchhiking stars/shrimp/crabs should drop out into the bin. Wet live rock is incredibly beneficial to a new tank because it has so many good things in it that a new tank really needs. Killing your rock will make it very difficult to cycle your tank.