Ifusing something like ceramic then isuppose its arguable that you can use that instead..but whichever way its dressed up it isnt as efficient andits 'trying'to replicate the real rock.makes sense to use the real thing unless such big differences in price that it stops people doing it properlyI started my tank with dry rock and have replaced most of it with synthetic dry rock. I have seen plenty of tanks over the years that had ZERO live rock in them and they looked amazing. I just don't believe it is necessary anymore.