DUH!
I made EVERY mistake possible in my trek through the watergarden adventure! Notable was way back when I made my first "goldfish" watergarden out of black construction plastic (EDPM was not available to me then, or for that matter, to anyone else, as a matter of fact, it was called EPDM from the 1960's when it was first employed as a roofing material.), and after a couple of years the pond began to leak. (Note, I still line plant ponds with construction plastic, but replace it every two years.)
Next in line was the first concrete pond I made. Of course it leaked. Concrete is not waterproof unless coated with cementitious material like gunnite or drylock.
My first attempt to create a koi pond out of concrete was done before I read up on the requirements of koi. After my 200 gallon pond was complete, I read about koi. Then I got out my 16 pound sledge hammer and cut the pond in half and increased its volume to 800 gallons.
I now have ponds lined with concrete, EDPM, and HDPM. I also consider myself an expert on the use of all three liner choices.
Over the years (How many since 1972??) I have tried out many filter system designs, some abject failures, some successful. My website indicates a working system although I have "tweaked" the designs since the site has been updated. There are ALWAYS improvements to be tried.
BTW, if you have installed Google Earth, you can actually make out a couple of my ponds from the satellite photos. (Type in 7501 Lawyers road, Charlotte, nc). The circular item in the backyard is my wife's herb garden. One pool is just straight up and a little left of it. If you follow the house roof line to the right, you will see the 2,700 gallon pool and just above it is the filter system ( the rectangular item. Plant pools can be seen along the fence line between me and the church property to the right. My other pools are obscured by trees.
If you don't look at your life as a journey, you are missing the point of it...