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The octopus, the aquarium's star attraction, mysteriously vanished from his tank last month.
Five frustrating days later, a baffled staff member spotted Sid making a dash for the door, said Tessa Mills, manager at the New Zealand Marine Studies Centre, which incorporates the Westpac Aquarium.
All the time, Sid had been using a seawater drain - part of the system used to pump fresh sea water through the aquarium - in a bid to reach the facility's sea water ponds outside.
"With a little gentle persuasion, Sid was finally back home in his tank, hungry but otherwise fine," Ms Mills said.
The sliding doors which provided access to a plastic case over his aquarium tank were now kept tightly closed.
"Once an octopus has learnt to escape, they have a tendency to continue escaping.
"We are still trying to catch a new octopus to replace Sid, who will then be set free."
Aquarist Dr Jean McKinnon said: "Sid's got quite good eyesight. We're watching him and he's watching us".
Aquarium senior aquarist Matthew Crane said an octopus's problem-solving ability made escape-proofing its tank "quite a challenge".
About 10 years ago, an octopus at the aquarium named Harry - after human escape artist Harry Houdini - escaped from the same tank now occupied by Sid, and was halfway up the steps to the nearby University of Otago marine laboratory when found.