I fail to see why there is so much worry about a little bit of tarnish of the 
electrodes. I never bother to clean them. If there is sludge on the cathode I 
just wipe it off.
   
  I have hundreds of experimental runs, all data plotted and there is no 
adverse effect to the silver oxide that is formed. In fact the silver black on 
the anode facilitates the transfer of silver ions into the solution.
   
  "Ole Bob"