Have you seen Caribsea’s South Seas Base rock? South Seas had much more structure than any other commonly available aquascaping rock and is much more porous than other as well. South Seas is a calcium carbonate base rock that is very similar to actual reef rock and at one point actually was, although it is obtained terrestrially from ancient coral reefs underground. South Seas will make the perfect alternative to live rock or can provide a very attractive base for live rock. A 40lb container is about $90, not bad.