I have eight 8 gallon buckets, a milk can, four 12-14 inch culverts, and two brush piles in my first 1/4 acre pond. I have no evidence that they have spawned. I have nothing more than rock, brick, and a couple brush piles in my second 1/4 acre pond, and no direct evidence yet that they have spawned there either. If they have, the BG probably eat the fry.
If I catch a yearling CC, I will post on here.
I know Snrub has had CC recruitment in his largest pond, but it's 3.5 acres with lots of cover, and aerated.