Cupid the first thing I would suggest is digging out some if not all the depth as this will help to regulate the temperature changes caused by weather etc which can be very harmful to fish, I assume you will be keeping fish in it?
Are you building the walls off a strip foundation or a slab, the slab option will allow the whole pond to move as one if there is any ground movement, at zero depth frost heave should be considered. Also slope the bottom to a central point as this will aid removal of waste, mine has a 4" bottom drain that feeds the filters.
Which brings me to the next point, unless you plan on heavy planting and a few fish you will need filtration and a UV if you want to see any fish.
For the curved unsupported wall I would lay the blocks flat to give a 9" thick wall and place Exmet in the joints to prevent cracking. Or use hollow blocks with rebar & infilled with concrete.
Here are a few pics of mine:
This one shows the 8" thick reinforced raft foundation, hollow blocks and 4" filter feed, the bottom was later sloped to the feed.
The blocks have now been infilled and an integral concrete ring beam cast in place to support the rockwork, you can see some Exmet joint reinforcement on the pile of blocks, corners "eased" with cut thermalite blocks, wall to filter bay added
Walls now rendered and direct fibreglassed, rockwork & waterfall in place, filter in chamber, surface skimmer bottom right of pond wall.
And a couple of finished pics, any other queries just shout.
Jason