Hot UK weather leads to pond fish deaths
The current hot weather in the UK is leading to an increase in fish deaths in garden ponds - an occurrence known as "summer fish kill". The problem is caused by low levels of dissolved oxygen in the pond water, and fish usually die early in the morning, with mainly larger fish being affected. During hot weather water is capable of holding less dissolved oxygen than at cooler temperatures, and if there are large numbers of fish, organic wastes or aquatic plants in the pond the oxygen levels can plummet to dangerous levels. To avoid problems ensure that your pond pump is running continuously, especially during the night, when oxygen levels drop dramatically.