How Many Watts Should My Aquarium Heater Be?

Fish are cold-blooded species. This means that they do not have the system to maintain their body heat and depend entirely on the temperature of their environments for healthy sustenance. Due to this very reason, you must install appropriate fish tank heaters for your fish. Here you will find list of Best Aquarium Heaters.

With the importance of aquarium heater established, the next step to follow is to determine the correct heater rating for your tank. You can have the best heater ever, but if you do not know how to choose the ratings of the heater, it will be of no use. The watts of your aquarium’s heater will determine whether or not your fish are going to live a healthy and comfortable life. To find out what is the accurate watt number that your fish tank needs, you will have to keep a few things into account. For your ease, we have listed down the factors you should keep in mind before choosing the right watts for your aquarium. 

Fish type 

Tropical fish thrive well in warmer water conditions, while cold-water fish can survive in a wide range of temperature conditions. Therefore, if you are keeping tropical fish in your aquarium, you need to make sure that the temperature of your tank is above 72°F/ 22°C. To maintain this temperature, an appropriate choice of fish tank heaters must be made. However, if you have fish that can survive in cold temperatures, you don’t need to install a heater.

 Tank size

Another thing to keep in mind before setting the watts of your aquarium heater is the tank size. It plays a vital role in the overall heating requirements. A larger tank will need more heating. For this purpose, it is essential to increase the watts of an aquarium heater. As a rule of thumb, for every gallon of water in your tank, there should be 3-5 watts of power available. For example, for a 20-gallon fish tank, you could have heaters with ratings in the range 20 x 3 = 60 watts and 20 x 5 = 100 watts.

Room temperature

The room temperature of the place you have kept your aquarium impacts the water temperature. So, to have the right watts for your aquarium heater, it is significant to know the room temperature. If your room temperature is usually high, you would not need high watts for your heater. Therefore, you should keep close attention to room temperature before making a decision. 

You can find out the amount of heat required by the tank by subtracting the room temperature from the temperature required by your fish. Generally speaking, for tank sizes greater than or equal to 75 liters, a 10°C increase, means the wattage of your heater should be equal to the number of liters of water. For example, to change the temperature of 150 L of water by 10°C, you would need a 150-watt heater. Remember that this is a rough estimation only, and precise determination is via trial and observation.


These factors should be enough to help you make the right decision. Just make sure that you monitor the tank water temperature carefully and regularly, and make sure that water is evenly heated. With these tips, you should be able to maintain the correct temperature for your fish.

Related Article : Best Aquarium Heaters Reviews.

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