Concerning pond and fish.
I'd guess I killed 70% of my fish from using clarifiers that reduced the O2. O2 GOOD low bad. This over perhaps 10 years. My fault and due to striving for clear pristine people wanting pond. Gave it up and now the fish thrive with one notable exception I hide it from the sky. Seems after camouflage was worked out a monster spotted my pond. Ate some whole and just took the eyes of the larger Koi. So my pond is well hidden now and the great blue heron who was very close to death has not come back.
The guy with cow and wife ideas is not well.