Invert die off, mostly

When I first started getting into planted tanks, part of the reason was that I really, really wanted to keep shrimp. After setting up my 55g and cycling it I dumped in a bunch of ghost shrimp with my fish. Over the next few days, many died off. Then they started dying off more slowly, one or two a day over the next few weeks. They acted normally, eating and molting, but would just die until none were left. A few months later I tried again, with the same results (some of them fell to my giant pig-bastard of a black skirt tetra, but not many). I also tried putting amanos and a couple nerite snails in my 10g CPD tank, with the same pattern. Eventually I only had one shrimp left, and he had lasted maybe 10 or 11 days, when he molted and then died the day after. The snails lasted about the same. I keep my water pretty clean, with regular water changes. The water is very hard though. I also live in an old farm house with a lot of copper piping. I spoke with a guy at a LFS and he thought that the copper might be the problem. I agreed, but now that I've thought about it, I have pest-snails from plant orders that I've made, that I've been fighting pretty consistently over a year. Are the little pesty snails hardier and more adaptable to trace copper or do I have a more fundamental problem? Any opinions are appreciated, thanks