Staff believe that the octopus called Otto had been annoyed by the bright light shining into his aquarium and had discovered he could extinguish it by climbing onto the rim of his tank and squirting a jet of water in its direction.
The short-circuit had baffled electricians as well as staff at the Sea Star Aquarium in Coburg, Germany, who decided to take shifts sleeping on the floor to find out what caused the mysterious blackouts.
A spokesman said: "It was a serious matter because it shorted the electricity supply to the whole aquarium that threatened the lives of the other animals when water pumps ceased to work.
"It was on the third night that we found out that the octopus Otto was responsible for the chaos.
"We knew that he was bored as the aquarium is closed for winter, and at two feet, seven inches Otto had discovered he was big enough to swing onto the edge of his tank and shoot out the 2000 Watt spot light above him with a carefully directed jet of water."
Director Elfriede Kummer who witnessed the act said: "We've put the light a bit higher now so he shouldn't be able to reach it. But Otto is constantly craving for attention and always comes up with new stunts so we have realised we will have to keep more careful eye on him - and also perhaps give him a few more toys to play with.
"Once we saw him juggling the hermit crabs in his tank, another time he threw stones against the glass damaging it. And from time to time he completely re-arranges his tank to make it suit his own taste better - much to the distress of his fellow tank inhabitants."