Rio Olympics 2016: Officials drain green pool before synchronised swimming
Rio's main Olympic pool will be drained as part of major work to prepare for Sunday's synchronised swimming.
The larger pool in the Maria Lenk Aquatics Centre turned green on Wednesday, a day after the diving pool had also changed colour.
Officials blamed high chemical levels, and divers were unable to use the pool as work continued to change the colour.
Rio communications chief Mario Andrada said a "more radical approach" was being taken to prepare the water.
"One of the measures is to replace a big part of the water in the main pool," he added.
The larger pool is used for water polo as well as synchronised swimming.
Gustavo Nascimento, the director of venue management, said clean water from a practice pool would be transferred to the main pool.
That was necessary, he said, to ensure clear water for synchronised swimming judges and competitors, with the majority of the competition taking place under water.
The diving pool will remain in use as officials say there are no health risks to athletes.
Organisers said adding hydrogen peroxide in an effort to clean the pool had caused algae to grow.
"This is a way of cleaning swimming pools but you're not supposed to combine it with chlorine," said Nascimento.