Copper Not as a Medicine

I lost one of my beloved mollies the other day and evidence has led me to believe that it was because of copper in the water. (The situation has since then been drastically improved). I have researched its effect on fish but if you would provide any information about copper either via links or writing it would be greatly appreciated.

Thanks for replying. I didn't realize that there was so much copper in the water. It has about 0.5ppm Cu! Scarry. I didn't think about it or notice until copper colored stains appeared all over my tank: on rocks, plants and my filter. I didn't know what it was at first but I tested, and sure enough...
I am now left wondering and thinking that the copper in the water here might be bad for the people that drink it too...