I added 10 Christmas trees to my 1.5 acre pond this past weekend. I scrapped the whole brake rotor idea and picked up 10 cinder blocks.
I placed one under each side of my bridge spanning between the two post in 3-4' of water, used zip ties to hold them to the post. One under each corner of my dock, I drilled a hole in the end of the trunk and zip tied a cinder block to it, then zip tied the top to the corner post just under the water surface so they are leaning at an inward angle.
I took two short ones (6') and drilled through the trunk and zip tied them to each side of one cinder block where they stand up in a V shape. I placed them where the 4' water drops off to 8-10' coming out of the cut to the bridge where just the tip is sticking out the water. I then took the remaining 4 and zip tied a cinder block to the middle of the trunk on each one so they will lay flat and placed them in a line running just above the drop off from the corner of the island to the two that are standing.
I'm not sure if any of that makes any since, but that is what I did.
