uncleof6
Active member
You are not reading it completely or correctly. A ground probe provides a degree of protection, at the expense of continuous current flow through the tank. In other words, you are subjecting the inhabitants of the tank, to a continuous flow of electrical current. Do you think you would enjoy having a continuous flow of electrical current through you 24/7? People get all scared and up in arms when they get a little tickle of current from a potential often as low as 12VAC! Sea critters do not have the same high skin resistance as us humans do, therefore they feel the electrical current flow far more than we do.
The rest of the story:
It is really simple actually. Ground probes create a path to ground, where such a path should not exist. It creates an extreme safety risk due to induced voltages involved with AC motors and HID Lighting. E.G. you grab your lights, pick up an induced voltage that will be above 40VAC, accidentally touch the water, because the water is now a ground, you die! The GFCI will not trip, nor will an AFCI, and neither will be aware of the misdirected current flow.
Grounding probes are the work of foolish marketers, that really don't know what the problem really is. They take advantage of hobbyists that don't understand electricity, or what the problem really is. It is certainly NOT stray voltage. The notion is ridiculous, and a symptom of the lack of knowledge concerning things electrical, especially the nature of ballasts, and how they are isolated from the line, making a GFCI useless when you grab the load side of the ballast.
This is a very hotly debated topic, but the physics of electricity is very clear and concise. Ground probes are a waste of your money, and give a false sense of security, just as using GFCI outlets for AC motors, and HID lights, give a false sense of security. The only real security is using common sense, and sticking your hand in the tank, while standing barefoot on wet concrete, is just really begging for a Darwin Award, even though the voltage potential, under normal circumstances will be far less than 40VAC, e.g. far less than potentially lethal.
The other common sense thing, is you are not supposed to be sticking your bare hands in a Marine system anyway. That is from Basic Aquarium Keeping 101: It is not to protect you, it is to protect the critters from the crud on your hands! The plus to you is you don't get electrocuted, if there is an impressed voltage in the tank, and the GFCI fails.
The bottom line, is there is no such thing as "stray voltage." There is however "induced voltage" due to the use of HID lighting and AC motors. These induced voltages are very low in magnitude, and non lethal, even if you do decide to grab the grounded copper wire and stick your hand in the tank. Sometimes there will be an "impressed voltage" (120VAC) in the tank, which does present a significant risk, due to damaged power cords for the most part, or broken heater.
Case study—the submersible ac motor:
An AC motor with an equipment ground, (e.g. a three prong plug,) already has sufficient protection for both the human and critter in the tank. If the motor shorts, it will trip the breaker (remember there is NO grounding probe,) so the critters would not be aware of anything, because there was no current flow through the tank, the current flow remaining local to the motor. Same with a shorted cord either hot to ground, or hot to neutral. Since there is no current flow through the tank, rather local to the short itself, the breaker trips, and no one is the wiser. The hobbyist would most likely scratch their head and wonder why the breaker keeps tripping. The last thing is an abraded line cord that exposes only the hot wire. This would cause an impressed voltage in the tank of 120VAC. With a grounding probe, the GFCI would trip. More than likely, the user would be scratching their head wondering why the GFCI tripped. Without a grounding probe, there would be no consequences, until one stuck a bare hand in the tank, while some other part of them was grounded. Which is asking for a Darwin Award from the get go anyway.
The problem can be avoided altogether by shutting down the system before planting your hand in the tank, which is the smart thing to do. The critters aren't going to notice the pumps aren't running for quite a while. The other smart thing to do is pay attention to what you are doing. All the safety gadgets in the world are not going to keep you from becoming a statistic, if you are the careless, preoccupied, and reckless type.
Speaking of statistics, according to the NFPA and Arson.org, the number one cause of loss from aquariums is fire, not electrocution. Of the electrocutions (means deaths) that have occurred, they were not related to the water, rather the snake pit of cords, and multi-outlet devices under the tank. (Which is why such devices are not listed for continuous use as they are in the aquarium hobby, due to fire and electrocution.)
In conclusion, no reason not to believe Bean, he is not given to frivolity, however for more perspective, see Robert C. Michelson, a professor at Georgia Institute of Technology:
http://angel-strike.com/aquarium/GroundingProbes.html
:fun5: 
