Guppies will die when the water temperature is lower than 10 degrees Celsius. Guppies are tropical fish, and the suitable water temperature range for them is from 20 to 28 degrees Celsius, with the optimal water temperature being between 22 and 24 degrees Celsius. When the water temperature is lower than 10 degrees Celsius, the metabolism of guppies will slow down and their immunity will decline, making them prone to getting sick or even dying.
To ensure the healthy survival of guppies, it's necessary to keep the water temperature within the suitable range. Heating equipment can be used to adjust the water temperature, especially when the ambient temperature is low. Besides, sharp changes in water temperature also need to be avoided. The change in water temperature within a day should not exceed plus or minus 2 degrees, otherwise it may have a negative impact on guppies.