I bet they weren't built by just pushing dirt. A properly constructed dam needs to be cored and filled with good clay. Then the soils and clay have to be "knitted" together. If not, a "seam" is left that lets water run under the pushed up dirt.
Mine was built that way before I learned how it ought to be done. And the dozer guy that I hired could do anything with his equipment but was ignorant as I was about building a dam that holds water. Mine will always leak.
It's not about the fish. It's about the pond. Take care of the pond and the fish will be fine. PB subscriber since before it was in color.
Without a sense of urgency, Nothing ever gets done.
Boy, if I say "sic em", you'd better look for something to bite. Sam Shelley Rancher and Farmer Muleshoe Texas 1892-1985 RIP