I wanted to comment on the article "Why Shrimp Die" at http://www.petshrimp.com/articles/whyshrimpdead.html
. It's a good article and I wanted to add some things.
You may think, from reading the article, that all shrimp you buy are going to be bad quality. But what the article said is most shrimp you will buy from *commercial institutions* are going to be bad quality. Why is this? They have to economize and stuff many shrimp into small shipping containers, and they get most of their shrimp from half way around the earth. That's a long way for a shrimp to be stuffed in a box.
The solution? Buy shrimp from a local or online breeder/hobbyist. They are not in it for the profit and they care more about how their shrimp are packed.
Also a note about meds and metals, like copper. Where can copper come from to kill your shrimp? Maybe your little brother threw a coin in the water and made a wish, then he thought he did something bad and covered the submerged coin with gravel. So the coin sits in your tank slowly killing your shrimp.
Perhaps you got a used tank and the previous owner used a copper-based medication in it. I have heard, though I can't confirm, that meds can seep into the silicone and then slowly seep out over time. This could be a clue to mysterious shrimp deaths. It certainly seems possible that meds could also soak into ceramic type ornaments and even wood pieces. (Gravel is sealed so should not be a problem.) When in doubt, remove all ornaments, do a water change, and see if shrimp deaths slow down or stop.
Perhaps you bought a cheap Chinese HOB filter. The impeller axle was not solid steel, it was actually chrome covered copper. Now the chrome is coming off, exposing the water to copper.
When diagnosing problems, the issues in the article above are the most common. But for more mysterious deaths, some deep thought is required, like "Where could copper possibly be coming from?"
Regarding copper sulfate in fish foods. Copper sulfate is safe for shrimp. I have been feeding foods containing copper sulfate to my shrimp for years. It is elemental copper, like from copper pipes, that is the problem.