All biOrb aquariums use safe 12v electrical supply to avoid any risk. Safety is vital when operating electrical items in close proximity to water. To protect the Fishkeeper and children from electric shock biOrb aquariums use a plug top AC transformer that plugs into your electrical mains socket and ‘steps down’ the mains 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. Special Note : The AC transformer is capable of handling a maximum of 20 watts power and incorporates a non replaceable safety fuse that will blow, permanently damaging the AC transformer, if a halogen bulb of greater than 20 watts is used to replace the 10 watt bulb supplied with the light.