You are welcome, Glad it worked out for ya!
Just curious and please dont take this the wrong way.
Are you an electrician or someone with an electronics background?
I guess I should have been more detailed here:
The GFIC monitors the current that travels through the circuit on the hot and neutral sides. If it senses more current going out than back in (a ground fault) it trips. This would protect you from shock if the light went into the tank and you put your hand in to grab it (thus creating a ground fault via your body). The current traveling through your body to ground would cause the GFIC to trip before you were badly shocked. You may feel a slight tingle but not enough to do damage.
However, It would not protect from the current overload of dropping the fixture into salt water. Saltwater is highly conductive. If the light were to fall into the tank with no ground wire then the fixture would short out and draw allot more current than usual. This current would not trip the GFI as it would be going out the same circuit it was traveling back down (no ground fault), this extra current draw could cause the wiring to overheat and a possoble fire in the hood, stand ect. Your circuit breaker would trip once the current exceeded whatever the breaker size was. 15 amps is typical and allot more than most light fixture wiring is designed for.
If there were a ground wire on the fixture than the current would flow down the ground causing a difference between what was going out the hot and coming back down the neutral. This would trip the GFIC.
If you had an in tank tank ground probe it would also cause a ground fault and open the GFIC.
Yes, I do have a strong electrical background.
The light would function fine with no ground wire to the socket. I just tend to error on the side of caution when it comes to electricity, saltwater and people's safety.
After all, if you are in the hospital or worse who is gona do your water changes :.
Hope this clears up any questions.