I gave this topic much thought when I setup my 180g reef. Some ideas to minimize risk of getting eletrocuted:
1. use grounding probes in the display, sump. cons: none
2. install separate GFCIs. cons: trip when away at work/vacation, whole tank dies of lack of circulation and temp extremes
3. use external returns pumps. also decreases heat, easier to service. cons: noisier, greater chance of leaks
4. use external skimmer. also easier to service. cons: less skimming power per amp, noisier, greater chance of leaks
5. use external/in-line heater. cons: only know of hydor 200w heater (not powerful enough), harder to service
6. use external powerhead (vortech). cons: expensive
7. use closed-loop. also decreases heat. cons: greater chance of leaks
8. place ballasts as far away as possible & above the water line (mine are actually through wall in the garage). cons: the sockets/bulbs still need to be above the tank, could still fall in.
9. use LEDs, less amperage=smaller shock. cons: expensive
10. use only inline chillers and UV. cons: none
Most of you must think Im paranoid. But after the high of having a successful reef wore off, I realized that the centerpiece of my house was also its largest liability. It could electrocute me, burn down the house (with me & my family in it) or cause tens of thousands of $ in water damage.