Well... http://www.theaquariumwiki.com/Copper
So, essentially, 0.03 ppm of Cu is enough to kill shrimps, I am afraid, if we trust the source. I have been looking for some works about toxicity. So far, I just found one study related to Penaus japonicus which is probably much less sensitive than freshwater shrimps: http://www.vliz.be/imisdocs/publications/33443.pdf
Main conclusion is that a concentration of 4 ppm is enough to kill 50% of those shrimps in 96 hours. And even less copper if you mix it in the same medium with other toxic metals (which is expected).
Nevertheless, I also doubt micro fertilizers will cause any problem. Note that the concentration of copper in micro ferts is a % in weight. If the ferts are dry, then this % will be reduced by the dilution into the bottle, plus also the dilution in the tank, so probably you are in the order of 0.001 ppms, or so. If you provide the data from the ferts and the dosing you plan, as well as the volume of the tank, I can help you with the maths. 😉
Cheers,
Manuel
I've steered away from the dry ferts, bought some TNC complete liquid