GFI strip from walmart
The GFI power strip from Walmart is approved for aquariums. For about $12 it is a great thing to have on each tank, if you are not able to replace the outlet with a GFI receptical.
You can also get a plug in GFI, I found one at Sears and at Walmart, but it was nearly as expensive as the GFI power strip. It is just a yellow thing that plugs in and has one outlet on the front and the test buttons. Not at all the industrial type.
It is a good idea to say you are not going to stick you hand in the tank when a light fixture falls in, but in real life, you will try to catch it even as you say "hey, that light is falling into the WATER, that may be dangerous" and the next thing you know you have your hand in the tank anyhow.
And, if a heater or filter shorts out and electrifies the tank, you may not know it until you go to clean the tank and stick your hand in, connecting to ground. That GFI will keep you alive.