Do I Need a Heater for Tropical Freshwater Fish?

Most tropical freshwater fish want roughly 74°F to 80°F (23°C to 27°C). Room temperature alone is too cold in many homes, especially overnight. A submersible heater with a built-in thermostat is standard equipment for community tanks.

Size the heater for your tank volume — about three to five watts per gallon is a common guide. Use a separate thermometer to verify the reading on the heater dial; stuck-on heaters have failed plenty of tanks.

After a water change, let new water match tank temperature before pouring it in. Log temperature in ReefDiary if you run a sensitive species or a room that swings seasonally.