Almost 8,000kg of glass are being replaced at Sea Life Blackpool.
Thirteen sharks and more than 300 fish have been removed while the new glass is fitted.
It is the first time in 23 years the tank has been emptied.
More top news
Victoria Station is set to remain closed until the weekend when bereaved families will be offered the chance to visit Manchester Arena.
Incredible scenes at St Ann's Square on Thursday morning, as people gathered to remember those killed in Monday's terror attack.
Friday could be our hottest day, but will the sunshine & very warm air from the continent continue for the North West over the Bank Holiday?