Great to have your input, Tom.
You are right, too often do we (myself included) say that shrimp are sensitive to heavy metals, etc, but it is all anecdotal
evidence and not factual
evidence as you have provided.
I myself have not noted any problems with shrimp deaths from EI dosing either; more often than not, I find my CO2 to be the leading cause of shrimp death
I actually do not KNOW at what level a SSS grade CRS might die due solely to Cu at a certain ppb/ppm level. There are many other factors that are dependent.
Temp, other livestock, other sources of stress/nutrition etc. So while say 0.08 might not kill them, it may reduce the brood production(never tested this) and might contribute to other stresses leading to mortality.
But these are speculations and should be viewed that way. They might be correct, but someone needs to demonstrate that with some certainty.
Fear is not a good method to rely upon.
We ALL do it(fear mongering) to some degree. But just being aware of the issues is much more helpful it would seem to me.