All aquariums need electrical power to operate their lighting and filtration systems and most use mains electricity at 120 volts. This can cause serious electric shock should the Fishkeeper drop or drench the electrical items in the aquarium water. The Reef One range of aquariums is designed to be extremely safe and therefore all its electrical items operate at the safe low level of 12 volts ac. To protect the Fishkeeper and children from electric shock, biOrb and biUbe aquariums use a plug top AC transformer that plugs into your electrical main socket and "steps down" the voltage to a much safer 12 volts AC. The 12 volts is made available in the bottom of the AC transformer through two din sockets. Either socket can be used for the halogen light wire plug or the air pump wire plug as both sockets are interchangeable. The LED light if used in place of the halogen light can be plugged into either socket.