@DR.V,
Yes, the pond-tank is approximately 700gallon, even though now I suspect it reach 800gallon. Still a long time to think and see about the fish.
@whitepine,
LOL... getting naked to maintain a tank.
@CardBoardBoxProcessor,
Worry not, this one is quite deep to the bottom (part that cannot be seen). 30-40cm cannot be too shallow.
Some pics, from last week.
The filter box is under further construction. Already you can see chambers taking shape.
From up close you need to sit or squat down to see under water and it is nice that you can pet with ease whatever fish you have.
A bit from a distance (right at the living room) a sofa or chair will do nicely as viewing point.
I decided the whole backdrop cliff decor will go right up to the opening, adding total height.