will gold fish die if its too cold
However, the fact that they are cold water fish does not mean that they should be kept in frigid temperatures. When water is too cold, goldfish may stop eating, begin hibernating or die.
Unless your goldfish live outside in a cool area, your fish do not need a heater. However, in cool areas, provide your fish with a pond heater and regularly monitor the water temperature. While goldfish can hibernate for a few months, if they're forced to hibernate for more than a season, they may die.