Thanks for the comment. It's funny indeed, petting your fish. He is a big fish, so damaging is not likely unleash you go slapping..lol.
For the big pond, lot of things to sort out. Houses are piled with concrete skeleton construction, so any wall can be removed and changed at will. Just stay away from the frame and you're ok.
Thing is, house is about 15 yr old. The ground seems to be stable now, early years there was substantial sinking of the land around the houses in my area.
However, we are in a river delta with a very high water-table. With recent flooding, water just pushed through the seams of the concrete base plates for the kitchen floor. So you can imagine that we have a very 'fluid' underground, in other words, there is quite some upward pressure from the water table.
The pond with water in it, will have a downward pressure of roughly 1500 to 1800 kilogram per square meter. For starters, I need to ensure that it will not crush the drains from the back of my house to the front.
1 solution could be to have 2 separate concrete structures with the area over drain pipe free, imagine it as a shoebox cut in half and separated leaving the opening free. Then the liner goes over it. When the pond does sink a bit, the drainpipe stays as is and the liner has some extra space to account for the sinking.
With the liner, this might be the easiest way to not press the drain down.
Of course, everything will be free, not attached to surrounding walls.