To clear up a few things:
A normal circuit breaker works by detecting the total current (measured in Amps) that's flowing through the line. If the total current goes over the breaker's rated capacity (typically 20 amps), then a little bar will get hot and deform, causing the ciruit to break, and the energy to stop flowing. This works fine for most things, but doesn't account for others. For example, dropping a hair dryer into a bathtub could send 19.5 amps @ 120 through the tub, killing the person bathing, but not throwing the circuit breaker. One characteristic is that the little strip of metal takes a little time (about a 1/2 second) to heat up and deform in order to throw the breaker. This works well for motors, ballasts, and other things that have a high inrush current. A normal breaker only monitors the "hot" line of a 2 or 3 line plug.
A GFCI is a Ground Fault Circuit Interupter. Instead of monitoring one line for total power, it measures the total electricity going to the appliance via the "hot" line compared to the electricity flowing back down the neutral line. (Yes, electricity in your house flows through the plug, just like a battery requires both leads to be connected). If there is an imbalance (as little as 4 or 5 milliamps), it will break (or "interrupt") the circuit.
A GFCI detects "leakage" of the current flow. A normal breaker only tests overall power. They're different devices for different needs. I don't run my chiller on a GFCI circuit, but I run everything else on one - the chiller has such a high inrush (startup) current that it'd throw the GFCI everytime.
To those who say that "a GFCI won't start back up"- neither will a regular circuit breaker. If it trips during a power outage, I'd argue that you have cheap outlets; I've never had one go off due to a power outage. My opinion is that I've got things more important than the running of my tank (such as my own life, my wife's life, and my house). If there's water hitting a live line, I want that circuit to shut off ie- "Fail Safe".
Finally, I have each outlet in my fish room as a separate GFCI, and wired appropriately, so that if one trips, it won't affect the rest of them. Combined with redundancy across circuits, pumps, lights, etc, even if one tripped, it may be a couple days before I even noticed....
