If I am you, I would boil everything first before I put it into your tank. You must keep it hot long enough to boiling temperature reach inside the middle of the rock. Rinse everything alive, that you want in the tank, with fresh sterile sea water. You can boil salt water then cool it down.
Doing this you will have animals you put into the tank on purpose and no hitch hiker. I am sure you can achieve what you want by doing this. Won't have a very interesting tank, IMO, and very difficult to keep stable, but with enough water changes, hopefully it can keep the fishes alive. Some of the invertebrates are a lot hardier, but "creepiness" is a death sentence so "creepiness be gone".