You are correct about the properties, however, we used brass ( part copper ) and we also used aluminum. However, once we were finished, we inoculated the water with 1 percent pond water and the organisms did regrow, showing that the water itself was not toxic.
Also, we have observed the microbes under the microscope. When they we almost to the point of blowing up, we turned the electric pulses off. TThe microbes recovered and swam away, proving that it was the electricity that was producing the effect.