You can dry or bleach the rock. Personally when dealing with the nusciense nems, no method is fool proof, but the bleach is the best. Rinse very well in freshwater after bleaching and realize that the rock will have to be recycled once you eliminated all the micro life. To bleach use about a 10% bleach solution.
As an alternative, you can eliminate these with kalk
paste, it takes a lot of time and due diligence to eliminate them, but not really any more than completely restarting and recycling your tank.
As far as building the rock structures, the best method I've found is to drill and connect the rock with acrylic rods. You can purchase acrylic rods as many home supply stores, and if you can't find any, you can actually cut the bottom section out of a plastic coat hanger and use that.