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.
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Sir Bruce Forsyth, Sir Cliff Richard and the Prime Minister have been among those paying tribute to Cilla Black following news of her death.
Grass pollen counts remain low for the new week. Some weed and fungal spores airborne. Grass season in decline
Wet and changeable start to the new week - very windy at times with blustery showers at the coast