I never really understood that (although I have something similar). All homes have GFCI built into the circuits. Assuming they are the same amp rating, how would an additional GFCI protector make a difference? It will should trip first if your aquarium stuff was plugged into that I guess but if it was not present, your integrated GFCI will trip exactly the same. I'm no electrical expert so I'm sure there probably is reason and I just don't know it.
Edit: it sure makes it easier to reset though. Those GFCI home circuits can be anywhere in the house. Although one can summarize that if you're tripping your GFCI all the time, its time to look for the cause and react accordingly lol.
Not all houses have GFCI breakers, that is a more recent thing. Also, GFCI and AFCI are different, but if you have a new house you could have a combo that does both.
If you have GFCI or combo breakers, there is no need to an additional GFCI, but you do need your tank grounded. GFCI watches power in on the hot, and power out on the neutral, and trips before the diff gets lethal assuming you are the path to ground. So, if everything you put in your tank that touches the water is 2 wire, GFCI will not trip unless your tank water is grounded, or you put your hand in and you are grounded well enough for lethal current to flow.
For my setup I have two plugin GFCI since I do not have GFCI or combo breakers. Each of those runs off a different UPS to a different power bar and I have alarms set for if a power bar loses power as well as critical stuff like heaters split between them so that one tripping does not take off all heat, or flow, or anything else critical. I also have a titanium ground probe. With that I caught a heater that shorted. The heater itself still worked, but water got to the hot inside of it, GFCI tripped, I got a text, and then I tested everything on that power bar one at a time till I found what was shorting out and replaced it.
In my view, GFCI is a must, and so is an alarm/alert system of some sort. Over long enough time something will fail and short, and the GFCI will trip. You need to take that into consideration when setting it up and make sure that when it does trip your tank is not shut off entirely with no notification being sent.
