Traffic banked-up along Tamaki Drive around midday as a truck delivered a large generator to Kelly Tarlton's Aquarium.
As staff and technicians rushed to get it working, a steady stream of tourists were turned away from the entrance.
Curator Andrew Christie told the Herald that there had been no electricity to power the tanks and enclosures since the outage early this morning.
He said staff were monitoring conditions in the tanks including dissolved oxygen levels. The generator would power some tanks, and Mr Christie said the fish and other creatures would be okay.
The generator would also power Kelly Tarlton's snow-filled penguin enclosure, which houses sub-Antarctic King and Gentoo penguins and is kept at about zero to one degree celcius.
Mr Christie said the penguins were not at risk. The area had kept cool, despite being without power: "It's like a big fridge".
Nearby, residents at the Grace Joel Retirement Village on St Heliers Bay Rd were taking the power outage in their stride, a staff member said. There were no issues with health care and the village was seeing if a generator could be sourced.