Instead of a wood chisel, get yourself a brick chisel, cutting board and a big hammer and bust up that rock!
Don't be shy, pound away till you are happy with the results.
I'm not happy mostly with necessity of destroying aquascaping, setting heated 30g container with powerheads for keeping removed rock and corals there, while I'm working with the bottom rock and during restoring aquascaping (hours!)...
Lucky you to deal with the soft rock! Reef Bones (at least my package) are impossible to crack this way - I spent more than 2 hours at beginning, trying to divide rock just in one place, using everything suitable for the task.
I would rather remove them in the tank. I did the total aquascaping destruction twice, and will do whatever it takes to avoid this.
Thanks for the good intentions, anyway.
Mostly non-photosynthetics and fine filter feeders. Life in my tanks: Define Your Reef.
:doublet: