john rutz writes:

and to top it off 25.00 for it, and I can go to Home depot or Lowes
and buy a 6 ft grounding rod for about 15 and make a dozem of em

Copper kitchen scrub pad $0.89

I know from reef aquariums that copper is highly toxic to invertebrates (sp).
I don't know if algae is more or less sensitive. So if you don't feed your fish
then this may not be for you as it might kill some natural food sources (this
would be especially bad if you expect fry to survive in your pond). Will also
probably kill some parasites.

I'm tempted to try a sponge. I still have a copper test kit left
over from aquarium days. Be nice to know some numbers though, for
algae, invertebrate and fish toxicity.