Can anyone share experience/calculations for a closed loop laid into a stream, please? Our contractor suggests digging a pond beside the stream and laying coils into the pond. I picture maintaining a pond, (i.e., removing silt, keeping out passersby, etc.) could require a lot more than having the loop(s) in the base of the stream under a layer of sizeable rocks (to keep the tubing from being dislodged during high water flows). Experiences and opinions welcome, please! Thank you!