I'm with jobob on this. I added copper a while back. Now I have a bunch of crabs, plus and arrow crab and some snails...if there was copper, they would be dead by now. Just make sure you get a test kit and test for copper before you put the inverts in. Personally, a lot of filtration and water changes got rid of my copper and there hasn't been a 'release' issue, ever. Good luck!!