Re: Grounding Electrode

Graphite may not be an ideal electrode for grounding purposes.
It has a relatively high resistance. I believe pencil graphite
is actually a composite with clay and I wonder if it would get
soft and mushy in water.

An ideal electrode would be gold or palladium plated. These
metals are very inert and will not dissolve or corrode and
have excellent conductivity. A cheaper alternative might be 
to use aluminum (ala aluminum foil). Although it is not inert, 
I suspect it is far less detrimental to plants than copper or 
copper alloys and it also has excellent conductivity. Iron or
stainless steel are moderately good conductors and might work
well enough with a short piece however, I suspect a heavy 
coating of rust would inhibit the electrical contact. BTW,
aluminum oxides are one of the constituents of clays. Hope
someone with a little more electro-chemical background can 
comment on the use of aluminum in an aquarium. Would aluminum 
ions be detrimental to plants?

Steve in Vancouver BC with clearing skies :-)