I mainly employed a dremel tool by using a noticed blad on it. went gradual as not to get it overheated or bring about it to crack, wound up with two caves rather than a single. Aquascape Discussion Aquascaping is just as much an artwork as This is a science. https://www.whofish.org/Default.aspx?tabid=45&modid=379&action=detail&itemid=301302&rCode=33