This started growing about a month after we got the original tank from the original owner cleaned up and and parameters better (still working on that) this is in the new 75gal and it seems to be doing pretty good as we were moving into the new tank we found two other smaller ones and broke that rock up and brought them over also one has moved into the sand and the other has stayed on its lil rock piece the one in the pic is about the size of a nickle it's really pretty.