A government claim that fish killed by the red tide are safe to eat was challenged yesterday. The algae forming the tide which killed the fish 'are equally toxic to humans', said Professor John Hodgkiss of Hong Kong University's Department of Ecology and Biodiversity. His warning came as it emerged some farmers had taken dead fish from the water, put them on ice and sold them. It was believed the fish were being sold on the mainland. The Deputy Director of the Agriculture and Fisheries Department (AFD), Yip Shui-ming, insisted: 'The algae excrete a toxin which interferes with the respiration of fish but is not toxic to humans.' Professor Hodgkiss said the toxin was gyrodinium aureolum, which he had found in tests on water in Hebe Haven and Tseung Kwan O. Pictures of the dead fish showed signs of the algae, which were found in similar cases in Canada and Australia, he said. 'The fish displayed red markings on their bodies as if they had been bleeding underneath their scales.' Although little is known about where the algae came from, Hong Kong's environment encourages their rapid spread. 'Heat, rainfall and nutrients added to the water cause the algae to multiply many times,' he said. It is estimated the algae can double within three days in current conditions. Fish farms attract it with food put in the water for fish. The red tide first appeared on March 19 at O Pui Tong in the northeast. It spread south, claiming $70 million worth of fish on 1,000 farms. It has now reached Lamma and is threatening Lantau. 'There is almost nothing one can do when the red tide is discovered,' Professor Hodgkiss said. But Democratic Party environment spokesman John Tse Wing-ling hit out at what he called government inaction. 'Red tide is something to be expected and the Government shouldn't just be sitting around waiting for it to happen,' he said. Dr Lawrence Lee Hay-yue, an independent candidate for the Legislative Council and former head of the AFD, visited affected fish farms on Lamma yesterday. He urged the Government to set aside more resources to provide fish farmers with low-interest loans to help them recover their losses. This would be in addition to the $10,000 aid subsidies distributed to 100 fish farmers. 'In the longer term, I would like university researchers to conduct a study to find a more reliable forecasting system,' Dr Lee said.