copper=death.. i'll attest to that. and yes inverts should be acclimated longer than anything else. 2 hours or more is best.
i jsut recently lost 18 out of 20 snails. a button polyp colony, an anthelia colony, and an anemone,. all within days of adding them.
tested for copper and sure enough there it was. this tank had been fw once upon a time, and was treated for ich...7 YEARS AGO!
hence the reason i am now in the process of buying and setting up a 75gal. and have to replace everything. all the rock substrate and pumps.