thousands of dead fish were found at a lake in huizhou city in southern china 's guangdong province on friday .
owner of a fish farm which operates from the lake says he found evidence the water was polluted with ammonia .
he claims the loss of 100 tonnes of fish overnight will cost him over 1 million rmb -lrb- £ 110,000 -rrb- in potential sales .
employees are working to save any live animals by adding salt to the water to restore the chemical imbalance .