At least you have a core and if you have good clay soil you may be O.K. I've had a couple of ponds dug without a core and the builder looked puzzled when I asked about a core. I had some seepage initially around those two small ponds 25 X 25 holding pond and a 1/10th acre pond) but no longer. The 25 by 25 pond is now part of another 1/10th acre pond. Cecil did you do anything or did they just silt themselves in after some yrs?

Do nature a favor, spay/neuter your pets and any weird friends or relatives.