Uh you could chop.... Or, you could do what I have done in the past:
Step 1) Break huge piece from Monti Cap.
Step 2) Throw in trash.
Step 3) Repeat weekly.
Seriously, I would not be concerned about breaking a boundary area around that clam as the caps I used to keep would grow 10-20 in^2 a week. I was so annoyed that after my last move I ripped it all out and nuked the existing portions on the rock with kalk.
Caps are worse than caulerpa in my eyes! He he