First of all thanks about for sharing your thoughts, it's really appreciated.Also, try to keep a really smooth substrate line across the front of the glass.
Yep it is petrified wood! Worked on the hardscape for many hours and went to 4 petshop to get the rocks I wanted.this tank is very beautiful! your use of petrified wood (that is what it is right?) was really smart, the hardscape is great!