Even if you take all the rock out, if you miss one freakin polyp they will return. [smilie=devil.gif] You may have to just trade the rock in for same size piece of cured rock. You can also trade out the biggest pieces with the most polyps on then then slowly kill small areas with kalk. Another thing to try is snap off the corals you want, take the rock out and give it a muriatic acid bath , get it rinsed really well then recure the rocks for a while, at least you can keep the rock if you like it. You can always take this as an opportunity to reaquascape the tank, break off the corals you want and trade in the infested rock's or......a nice blow torch works well. [smilie=rofl.gif]
Good luck bro,