Nanometer-thin coatings of polyhydroquinone (PHQ), which release and absorb protons upon oxidation and reduction, respectively, were tested for electrochemically induced anti-biofouling activity under the hypothesis that a dynamic pH environment would discourage fouling. Antifouling tests in artificial seawater using the marine, biofilm-forming bacterium Vibrio alginolyticus proved the coatings to be ineffective in fouling prevention but revealed a deceiving artifact from the reactive species generated at the counter electrode (CE), even for electrochemical bias potentials as low as |400| mV versus Ag|AgCl. These findings provide valuable information on the preparation of nanothin PHQ coatings and their electrochemical behavior in artificial seawater. The results further demonstrate that it is critical to isolate the CE in electrochemical anti-biofouling testing.