yup agracrete. Ive made it before thats why I said my busted up life tree looked like it. I made a pillar and a background using egg crate in my 75 I had so long ago. BTW I did manage to recoupe about 50% of the cost of that life tree after a restock fee and return shipping. Never doing that again.Years ago before life rock . There was a lot of people making rocks with Portland concrete , oyster shells and mixing in large pieces or salt that will dissolve to make the rocks porous after cured .
I believe life rock is similar