The amount of current needed to give a person an electric shock is surprisingly low. With a 240 volt supply, a current of only 10 milliamps through your body to earth can give a painful shock, and a current above 50 milliamps is likely to be fatal. Not very much when a 200 watt beater draws something like 800 milliamps. While the possibility of a dangerous failure in modern commercial aquarium equipment is very, very slight, nevertheless a risk still exists. I've never seen any report of a person being killed by a shock from their aquarium in Australia but I have seen a report in an English newspaper of this happening, and have vague recollections of reading that several people die each year in the U.S.A. by electric shocks from their aquariums.
If your aquarium equipment is plugged into a normal household switchboard, with standard circuit breakers, it is highly unlikely that they will cut-out in the event of a fault in the equipment leading to a possible leak to earth of the low magnitude needed to cause a bad shock. Fortunately there is a simple, but unfortunately fairly expensive, safety measure which can be taken. This is to install a CORE BALANCE EARTH LEAKAGE CIRCUIT BREAKER, or ELCB for short, into the wiring system for your aquariums.
These devices work by continually monitoring the current in both the active and neutral wires of the circuit, and if a fault develops in the circuits leading to the leakage of current to earth, then the device instantaneously breaks the circuit. They are set to break the circuit only above a certain current loss, since some home appliances such as water heaters and freezers naturally have small current losses. The cut-off level ranges from 10 milliamps to 30 milliamps, with 30 milliamps being suitable for the aquarium.
Three types of ELCB are available. The first is wired into the main switchboard of a house and can give protection to all power points in the house, not just the aquarium power point. I'm not sure of the cost of this in Canberra, but with installation by a qualified electrician, it could be around $200 or more.
The second is a wall mounted model, which is a straight replacement for a standard wall socket and looks very similar. Installation is straight forward and most would feel confident about doing the work themselves The only possible complication is if the socket is part of a ring circuit with more than three wires going into the socket. If in doubt, get an electrician to do the installation. The cost of a wall mounted model is about $80 at one of the specialist electrical shops at Fyshwick. They are rarely to be found at the general hardware stores.
The third type of ELCB are portable models. These are self-contained units which plug into a standard socket and into which you plug your aquarium equipment, similar to an extension cord. They have the advantage of being able to be used wherever needed around the house, for instance with power saws hedge trimmers etc. but are quite expensive. The only one I've seen in Canberra was over $100. If you would require a wall mounted model to be installed by an electrician they may be worth considering, but their portability is largely wasted in an aquarium setting because it is virtually never free to use for other applications.
