Hi,

thanks for spotting and fixing this!

I knew that things like retaining walls etc do have a direction but in this case it seems that I forgot to set it properly.

About the flow of the weirs, I think it's by design but, surely, the wind can help ;-)
You can find some more info about the pond design here: https://rietland.com/en/pond-filtration-built-by-tour-taxis-brussels

Cheers