Definitely will add that to the to-do list.
Generally, you have to be a bit unlucky to die from a shock from a fish tank. Probably would have to complete a path across your heart.
So, if the circuit to ground is not completed until you touch the tank, I assume that the GFCI would stop you from being shocked for too long. The time delay for the GFCI to open would be good to know. I guess that if it is complies with Underwriters Laboratories it is good-to-go.
Anyone ever shocked with a GFCI in the system.
Side note: IME, shocks hurt much more and are more likely with saltwater.