Extra measures are to be implemented in all public swimming pools to fight off pest infestations. The Director for Leisure and Cultural Services, Anissa Wong Sean-yee, announced the measures yesterday after the discovery of bloodworms at swimming pools in Shamshuipo Park a day earlier. 'We will strengthen chlorine in the pools at night after closure to fight off the mosquitoes and other insects,' she said after a tour of the pools with experts from the steering committee on the Management of Public Swimming Pools. 'Secondly, we will create some movements in the pool water to make it harder for mosquitoes and other insects to lay eggs.' Pool staff would also be told to clear debris and increase the chlorine level of the pools after rain, while pool drains would be cleaned more regularly. The pools in Shamshuipo were closed for 11 hours on Friday after 90 bloodworms were found in three of the park's pools. Ms Wong said it was an isolated case caused by the recent heavy rains. 'Some leaves from trees around the pool fell into the pool. Such circumstances may have led to the eggs of some mosquitoes being found on the poolside.'