A quick video about how I've added a bog filter to a stream in my latest pond addition to my yard. In the video i mention a few items i used to construct the filter. Below are some links that may be helpful.
Drainage pipe for bottom of bog filter- https://www.bunnings.com.au/everhard-230-x-1200mm-small-evertrench-drainage-trench-liner_p4770446
Hex cell- https://ausdrain.com/30mm-hexcell-drainage-cell//
EPDM Rubber liner Firstone Pondgard (Amazon afflitate link)- https://amzn.to/3P7vcKg
Non-woven geotextile underlayment (Amazon affiliate link)- https://amzn.to/3zKWn81