Angelfish need a heater.
Angelfish are small and brightly colored ornamental fish that have certain requirements for water temperature. Generally speaking, angelfish are suitable to live in an environment with a water temperature of 22 - 28°C (or 24 - 30°C), and the most suitable temperature is around 28°C (or 28 - 30°C). Since the temperature varies throughout the year, especially in winter when the air temperature is low, a heater is needed to keep the water temperature within the appropriate range to ensure the healthy growth of angelfish. Therefore, a heater is one of the very important pieces of equipment for raising angelfish. When choosing a heater, you need to determine the power and type of the heater according to the size of the fish tank and the required water temperature.