I doubt that the amount of leaching out from the wood would amount to much. I have trout in my pond, and treated an area with Cutrine Plus with no ill effects to the trout.
The rocks might not make it to the pond bottom, but I'll bet they will sink into the ground over time. What about using the rocks for the majority of the path, but a 6'-10' bridge to let the water flow between the 2 areas? Rock walkway on both sides, bridge in the center? You wouldn't need more than 9 posts, and that's a bit of an overkill depending on how wide you make it.
I never thought of a bridge in the center with a rock walkway on both sides. Not only would it allow water to pass under it, I think it would look really good too. Thanks for the idea!!
