FISH farms are facing the most devastating red tides in history, with about two-thirds of farms already poisoned and losses estimated at $70 million. Seafood prices are expected to rise as most of the dead fish were almost fully grown, reared for summer sale. Desperate fish-farm owners have urged the Government take action to stop the invasion of the fast-breeding micro-organisms. 'It came so quickly I could hardly detect it,' said Leung Kun-wah, who operates a fish farm at Lamma Island's Lo Tik Wan. 'I woke up in the morning and tonnes of fish were dead. It cost me $400,000.' Some 1,000 of Hong Kong's 1,500 fish farms have been affected by the red tides which first invaded O Pui Tong on March 19. The suffocating organisms spread to Sai Kung and Lamma Island yesterday. Hong Kong Fish Culture Association chairman Wong Yung-kan described the situation as the worst in local history. 'Unlike previous tides, which were over in three or four days, this year it has spread out like an infectious disease. Preliminary estimates of loss are up to $70 million,' said Mr Wong. 'Fish eaters will probably have to pay higher prices in the coming months.' More than 100 farm owners have received $10,000 emergency aid subsidies from the Agriculture and Fisheries Department since the red tides emerged. A conservation expert said the micro-organisms, known as dinoflagellates, bred tremendously fast when the water temperature rose to a certain level. 'They breed so fast that their number can double in an hour. During the breeding process, they acquire a tremendous volume of oxygen and release toxic substances which suffocate fish in the farms,' said Alex Yau Shuk-kau, senior conservation officer of World Wide Fund for Nature. Nitrogen and phosphorus released by sewage at sea and artificial feeds used in fish farms also help fuelled the growth of the micro-organisms, Ms Yau said. She warned fish-farm operators to diversify their operations to minimise their losses and to monitor water temperatures closely so they could pump oxygen into the water at the first sign of a red tide.