Like was said, if the bank is steeper, (steeper than 4:1 in my opinion) you might want to make a "curb" where you want the rock to stop at, or it might just find it's way to the bottom of the pond.

If you don't put down geotextile fabric under the rock, it'll work it's way into the soil over time. Smaller rock will work in quicker than larger rock.

Larger rock, if below the waterline, will provide habitat and cover for invertebrates like crayfish. They will be able to hide between or under the rocks.

Smaller rocks pack too tightly together and don't leave room for them. I've seen RES making spawing beds on 3/4"-1" river rock beds.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).