Sumps are a great idea but it's important you don't get too many fish crowded into them and have low oxygen issues. The big governmental hatcheries usually run fresh water into them as they are removing the fish. And they are lined with concrete.

I wish I had build them in m two hatchery ponds! I did dig a small one by hand on the deep end of one of my small ponds and lined it with concrete blocks. Works good but would work better if it was bigger.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.