I just found a stronghold that I want to turn into a base, but I also want to keep the silverfish spawner. The problem is that the silverfish I don't kill hide in the blocks and keep breaking them. Are there any blocks that they can't break and if so which ones so I can line that part of my base so they stop breaking the walls. Thanks.
They only hide in special blocks disguised as stone brick, mossy stone brick, cracked stone brick, stone, and I think cobblestone. They won't come out of normal blocks of this type, so any of those blocks you place would be safe. Also, silverfish blocks take less time to break, and silverfish blocks disguised as stone actually take a bit longer. It might actually be good if you just kept killing silverfish in order to clear away all of the silverfish blocks, and then you can go back and replace them afterward.