How do you keep fish tank water warm?

Use a heater. A heater is the most common and effective way to keep fish tank water warm. Submersible heaters are available in a variety of sizes and wattages, so you can choose the one that is right for your tank.

Place the heater in the correct location. The heater should be placed near the bottom of the tank, where the water is coldest. It should also be away from any direct sources of heat, such as sunlight or heating vents.

Set the heater to the correct temperature. The ideal temperature for most tropical fish is between 75 and 82 degrees Fahrenheit. You can use a thermometer to monitor the temperature of the water and adjust the heater as needed.

Cover the tank. A cover will help to keep the heat in the tank and prevent evaporation.

Use a filter with a built-in heater. Some filters have built-in heaters, which can be a convenient way to keep your fish tank water warm. However, these heaters are not as powerful as submersible heaters, so they may not be suitable for large tanks or tanks with a lot of fish.

Use a temperature controller. A temperature controller can help you to maintain the temperature of your fish tank water within a narrow range. Temperature controllers are available with a variety of features, including adjustable temperature settings, timers, and alarms.