Staff at the National Sea Life Centre in Birmingham worked round the clock to prevent tropical fish and sea turtles from dying after a power cut which cost city centre businesses tens of thousands of pounds.
Parts of Birmingham including Brindleyplace, where the centre is based, were plunged into darkness at the weekend after a fire at the Ladywood primary Central Networks substation.
West Midlands Fire Service attended the blaze, which started just before 2 on Saturday morning and affected 8,500 electricity customers in the area.
By midday, only 13 customers were left without power, including the Sea Life Centre.
The centre was forced to rely on an emergency generator for 24 hours as temperatures dropped in tanks containing two giant turtles, sharks and thousands of rare tropical fish.
Special heating equipment was brought in to ensure the water temperature was kept sufficiently warm.
A spokesman for the centre said tropical fish and marine life needed to be kept in water heated to 25C (77F). He said if that temperature had dropped to below 18C (64), their lives would have been in danger.
Five Bangai Cardinal fish were the only casualties and have now been placed in quarantine because of their condition.
General manager Ian Crabbe said: "It was an extreme and difficult situation.
"But staff were determined to ensure none of the creatures suffered and I am proud of the way they responded to the emergency."
The cut also saw Christmas parties cancelled as restaurants in Brindleyplace were left without power. Neighbouring restaurant Bank spent the day informing diners that their celebrations could not take place.
Manager Brett Boyers, aged 28, said 500 customers had been booked in for the day.
"We have lost a lot of business, we think, in the region of #40,000," he said. "There were Christmas parties and someone was due to celebrate their 21st birthday.
"We are trying to relocate the diners to other establishments."
A Central Networks spokeswoman said its engineers connected generators to the substations on the Brindleyplace site and carried out repairs on the network.
She said the Ladywood station supplied ten substations in Brindleyplace, eight of which were high voltage customers. Five of these had their own emergency generators.
She said: "We finally got everyone back on at 1.09am on Sunday.
"A total of 8,500 customers were affected, to start with. Once the fire service had made the substation safe, we were able to get most people back on with 13 customers left - many in Brindleyplace by midday Saturday.
"We had to do a permanent repair and that is why it took so long.
"Due to the nature of the Brindleyplace circuit, which effectively loops back on itself to and from the Ladywood primary substation, engineers had to work through the day to dig down to the cables that fed the customers directly, test them to make sure that they had not been damaged by the fire, physically cut them and then attach them to working cables, without overloading that part of the network, to return to power."