Thanks guys for the reply. I have copper pipes, but I've been told that that shouldn't leach off. I do plan on having inverts, that's why I'm worried. Shrimp and hermits. I used Red Sea's test kit, which I've been told is pretty poor, so I ordered the one from SeaChem (whom I've had good luck with in the past) and I should have it re-tested by the weekend. I'll test the tap water to, just in case it is that. I added carbon to the filter, which I will be removing today after a three day run. If it still tests positive for Cu, I'll try that ph drop method. Thanks alot.