much iron can probably create a magnetic field, with obvious abnormal growths (you have never been diving near a shipwreck? them well then there are fish singular)
copper is very expensive: lately, and I'm gearing up to play my tools to work with scraps of old gutters and copper pipes.
also if we use other help for the growth of plants can be very useful in :
"ERIM" build their own do not buy it
http://www.planetpeace.altervista.org/erim.htm
(the assembly instructions have an error the base must be like the first photo at the top and an aluminum base that is used (the one to make the pudding)
good job.....