If I bought a house that happened to have a swimming pool — not my favorite landscape element — I would hope that the feature would be geometric, at least. If it instead were kidney-shaped, I would fill it in with loads of sand and peat moss and turn it into a garden of the prettiest swamp flora, full of pitcher plants and Japanese and Louisiana irises.
If the pool were a much preferred circle, square or rectangle, I would make it uniformly 22 inches deep, grow lots of aquatic plants in containers, throw in a few small koi and spend the years watching them grow.
I have no intention of doing this, by the way, because I already have a pond. My garden would seem lifeless without it, however, I would offer this general advice about decorative ponds, besides the shape. Make them bigger than you think you need. Small ponds are harder to keep clean and algae-free, and the water temperature fluctuates too much for the good of flora, fauna and owner. Another hard-earned lesson: Set it up so that the pump and the filtration box sit out of the water. This will reduce maintenance further and keep you out of the pond.
No ornamental pond is complete without waterliles. Part of the magic of a waterlily is that its flower inhabits two realms. It is born in the submerged crown and journeys upward to the dry world, where it opens to the delight of the aerial circus of pollinators and to the thrill of the gardener looking for beauty in the heat of summer.
