Citric Acid may be a good additive:
http://en.wikipedia.org/wiki/Citric_acidhttp://en.wikipedia.org/wiki/Chelation It appears to be a water softener and contains a mixture of Oxygen Hydrogen Bonds.
Cleans rust off of iron!
I believe I tried it one time in a very small cell, it make a huge amount of bubbles (like soap) but the bubbles did not break down to fast and made a large head of bubbles on top and out the tube. (This was a small cell with-out much headroom).
Anyways I thought bringing this up may stir some interest and get some feedback.
A easy way to get this is from citric fruits.
I have a bag of citric crystals, came with another solution I purchased for health reasons.
It should be easily obtainable as it used in many industries and has a lot of uses.