You wouldn't want to just charge the water in the tank. It is similar to the aiptasia zapper idea. The + and - are not connected, but hooked to different pieces of metal. Click the links in the article. This is electrolysis of saltwater. I am guessing the electrolysis separates the ions in the water and makes them more accessible to corals. Sounds like a fun experiment and I have plenty of equipment. My big concerns in a contained system are rust and evaporation.