yes, the pond will support koi, but koi are VERY hard on a pond. They love to dig and root in the mud on the bottom and sides of the pond and will keep it muddy. People who raise koi in "mud ponds" only keep them in the ponds during the summer and then move them to greenhouses for the winter. During the winter, a lot of work is put into reparing the pond and liming it to kill off parasites. Also in a natural pond, predators are much more of a problem. But yes....the pond will support koi. I suggest keeping the stocking levels low (to minimumize damage to to the pond). Congrats on your new place....it sounds wonderful!