As an electrician's son and former chemistry major (with plenty of physics in between) I should probably know this for certain, but I think there is likely a big difference between passing a small amount of current between an anode and a cathode (presumably using seawater as the electrolyte with the resulting electrolysis causing the build up of calcium carbonate) and the stray voltage we can measure in tanks...
Disclaimer: I *think* have a handle on most of the basic science here, but please correct me if I am wrong as I do not want to mislead anyone...
Our tanks build up a small amount of stray voltage because there is a ton of electrical stuff in our tanks (and their corresponding electrical fields) but no ground to discharge it to. Since glass is a pretty good insulator, the air/humidity around the tank is the only place for the voltage to dissipate to and air is a pretty miserable conductor as well (i.e., there is practically nowhere for the extra voltage in the tank to flow to). Therefore, we can stick our arms in a tank flooded with "stray voltage" and as long as we do not touch something that will ground us we will not feel a shock (i.e., at that point you are a bird on a wire... and so are all of your fish and corals).
Most times that damage or harm seems to occur from electricity in the tank (at least in the experiences I've heard about), it is because there is current moving through the tank... for example, you touch the grounded outer casing to your light fixture with your hand in the tank and get zapped (you are suddenly a conductor between the tank water and the ground on your light fixture) or a short happens in one of your pumps and a grounding rod provides an outlet for the current being pumped into your tank (where your fish and corals are suddenly part of the circuit because saltwater is a conductor). In theory, a GFCI would be able to detect both situations as a drop in the current going into/out of the outlet and would trip (saving your life and possibly your fish... which is why everyone should be running their tanks on GFCI's...).
All this said, if my understanding is correct (and again, I probably only know enough to be dangerous here... so please correct me if I am wrong), the situation they are creating in the ocean with the electrolysis is far different from what we are "naturally" observing in our tanks. That is not to say that we could not easily replicate what they are doing in an aquarium... if the idea actually holds any merit.
And MVlk... nice avatar... and you can't say I didn't warn you...
. Gotta love Friday's. Not enough brain power left to make sense of anything, but an overwhelming feeling of relief that you are free for a few days...
