Hi, I have been lurking and making foil hats.

I need help please. I have to remove the top two rows from the bottom two rows on the second chamber of my pond. The blocks are cemented together. Do I drill in between the blocks to weaken the mortar? Chisel? I don't want to take a sledge hammer to it. The bottom two blocks will need hold my DIY bio ball bakki shower. Long story this pond is 18 years old and I build it.
Also What issues will I have using untreated pine in contact with the water? I have read it is ok. It will be the same pine that I used for the frame to cover my pond past winter. It stayed moist from the humidity and still looks great. I am aware that it will rot and I will have to keep an eye on it.
I checked into aluminum L channel. I don't feel like messing with cutting and welding $$. I need to have a new pond build but now I will have to get by with the one I have.
If does not make sense let me know I am enclosing pictures to help describe.

Thanks, Lori