In the end, for the balance of the turtle and tortoise ponds I concluded a simple pond, made out of concrete, would be the best option for now.

Unlike the first pond, this one would not have a concrete frame, and in essence would be just a dished out area of dirt, covered in an inch of concrete, with a sump and a drain. They would be round and roughly the same size as the 3-foot kiddie pools, but not nearly as deep.

With a gentle slope on all sides and the middle being the deepest spot at between 6-10 inches, these ponds provide enough water to completely immerse but are easy to get into and out of. Generally speaking, they resemble super-sized bird baths.

These ponds, roughly 3-4 gallons each, took very little time to excavate, with the augering of the sump area taking up most of that. Each pond used between 1 and 1-1/2 60-lb bags of quik-crete, providing a base that was 1-2 inches thick.

I formed a small lip around the edge of the pond to allow rainwater to flow around the pond instead of into it. I did not use any reinforcing wire or mesh with the concrete, and I am certain that someone standing on them would likely crack them. But they were designed for turtle foot traffic rather than human, and if I decide on a better "ultimate pond" later, they can be readily broken up and removed.

These have worked well so far, but winter arrived more quickly than anticipated, so I was unable to do much analysis before the turtles started burrowing for the winter. With spring only a few months away, it won't be long before they are put to the test.