We are building a 20'x20' formal koi pond (concrete block and liner
inside, brick outside above ground), 6' deep with a 6' radius
semi-circle upper pond/falls. The brick will be capped with a 2"
Bluestone or Limestone coping.

We can't decide how far above the ground to extend the main pond.
Most importantly, we want it to be structurally sound (water/ice
pressure in Upstate NY). Also, we want it too look nice (i.e, not too
much brick showing so as to be overwhelming across the 20' expanse).
Finally, we want it to be functional for sitting next to and in order
for adults and children to view the plants, feed the koi, etc. We
will make the upper pond 1' higher than the lower one.

Any input would be much appreciated.
Thanks!
Dennis