I think the majority of your question was answered but I think a couple more things should be said.
Ground fault is a term referring to a short or leaking electricity making it's way to ground unintentionally. When you have leaking electricity and it gets grounded, that is a ground fault.
GFCI (ground fault circit interrupter) outlets and breakers detect flow of electricity and will trip (turn off electricity) if they detect a drop in electricity flow. So with the GFCI outlet you have, it is monitoring flow of electricity and will turn off the electricity if there is a sudden drop in flow.
An example of this is lets say your heater breaks in your aquarium and is leaking electricity into the water and you don't know it. When you put your hand in the water it is possible that you will be the ground and electricity will flow through you (you'll get shocked!) The GFCI will detect this sudden drop in electricity flow (ground fault) and trip and prevent you from a serious electrocution. GFCI and and arcfault type breakers essentially do the same thing but are more expensive.
Another option is to install a GFCI outlet in the first outlet box out of the breaker box, then all the rest of the outlets in that string will be GFCI protected.
The area that seemed kind of gray to me on this thread is that I believe the question was, "Am I overloading my shock buster by plugging all these things into it" and I think it was stated that if it was overloaded, it (the shockbuster) or the breaker would trip. This is not entirely accurate, a GFCI is not a circuit breaker, it is a ground fault interrupter. If it is overloaded, it may not trip because this is not what it is designed to do.
If your Shock buster is rated at 15 amps but it's plugged into a 20 amp circuit, it is possible to have the shock buster overloaded and not trip your breaker, the GFCI shouldn't trip because a ground fault (a short) has not happened. That's a little confusing but valid. Compare this to plugging a space heater into a cheap extension cord, the breaker won't trip until the cord has failed (melted / shorted).
All you need to do is determine how many amps all the devises your using on your aquarium pulls and make sure the total amps are not higher than the shock buster is rated for. If you plan to use more than one shockbuster or power strip and you know your not overloading them, still add up the amps between the two of them and make sure the amps are not higher than your circuit breaker.
I think you already had the answer you needed but just in case I wanted to cover it a little more detailed on a couple of the subjects. Hope it helps (and not add more confusion).
Joel