Actually, copper as a malleable metal works well. And as a conductor, it is terrific. I am just not sure about what alloys are also in this rod, and as you indicate, I am dubious about having copper dissipating into water with your feet expelling, *and* absorbing, stuff.
I will do more research. But it does occur to me that if we can hold on to copper electrodes for things like zapping and rife, ermmmmm... mebbe good for here too.
WIll likely defer to stainless steel to be on the safe side. Someone suggested platinum, but I will wait for someone to send me a couple platinum electrodes so I can try then out... heh.