Just out of curiousity, does my underlined and colored text above apply if the aquarist is not grounded? Sya the above scenario were to happen if I was standing on a dry rug on a wooden floor, would electrocution still potentially happen? . I have always been under the impression that the aquarist would also become the "bird on the wire" in the case there was no ground.....
The "bird on a wire" scenario, is used in reference to a conductor with current flowing. The bird on the wire is not completely immune to the current flow however, as the bird on the wire is a parallel current path, between his left foot, through the body, and out his right foot--or vice versa. The resistance is rather high, so the current flow is low, but still present.
In your underlined scenario, I would say no, it would not electrocute you. Since it is unlikely that current would be flowing through the tank to some other point, and would merely present a "potential." If current were flowing in the tank, it would still not electrocute you, merely by placing one hand in the tank--two hands in the tank would make you the "bird on the wire," because the conductivity of the salt water is far greater than that of the human body. Where it less, you would be the wire, with a bird on it.
However in this scenario, placing a hand in the tank, and contacting a "ground," would be a very shocking experience. To be electrocuted, (which means killed) the current has to cross your heart.
Voltage potential.....
While knowledgeable people are here, can this term be explained? It is wat I was told I felt when I reached my hand into a sump on a wet floor in a basement, but had no GFI trip. Through process of elimination, the cause ccame down to a Reeflo external pump. This was a tingling felt in small cuts on my fingertips....
Electrically speaking, voltage and potential are the same thing. The difference however is the usage. Voltage referring to doing work with value for calculations (ohms law) and potential being the "ability" to do work, or relating one reference to another.
Simply put, if there is a difference in potentials ("potential") it is measurable in the unit Volts, and if the two are connected, you can be certain current will flow, if the resistance of the connection is anything less than infinity.