We did some testing today using electrodes made from galvanized steel plates used to couple wood beams in building houses. they are about 8 inches by 5 inches and riddled with holes for nails to go through. We ended up with the zinc coating coming off, and into the water, but they worked pretty well, I was impressed.
Configuration was:
+nn-nn+
I spaced them out with tie wraps, so they are evenly spaced.
Looks like a pretty solid design, we might try +nn-nn+nn- to see if it works any better.
-MP