Concepts for building a natural pool + tilapia-duckweed self sustaining and self filtering ecosystem

Well guys, it's summertime for many of us! The kids are back at whining about wanting a pool and us forward-thinkers might consider such things as a double whammy opportunity for building the kiddos a natural pool that can double up as a self sustaining fish farm.

I see that a lot of work and studies are going forward in "third world nations" where they're turning tilapia-duckweed ponds into self sufficient dark (waste) water treatment facilities. I'd like to do something maybe NOT so drastic as this and just create a natural pool system that collects rainwater and runoff water into a small pond that keeps the water healthy and stored for both tilapia and duckweed growth as well as human drinking (with of course some filtration) and consumption.

Has anyone seen any particularly successful builds or plans of this nature? Or have you had success with this?

I think I'll be digging (ha ha) into this project within about 1-3 months, so I'd like to do my homework now in laying out some plans and finding out what has worked and what has not worked.

I follow both https://naturalswimmingpools.com/
and  http://www.organicpools.co.uk/

The second one sells instructions for self build organic ponds.