Aquarium Heater Size Calculator
Aquarium Heater Size
Calculate the heater wattage for your aquarium
gallons
F
F
Formula
Wattage = Tank Volume (gallons) x Watts per Gallon (2.5-6 based on temp difference) x Location Factor
Frequently Asked Questions
How many watts per gallon do I need?
The general rule is 2.5-5 watts per gallon, depending on the temperature difference between your room and target water temperature. For a small difference (under 5F), 2.5W/gal is sufficient. For larger differences (10-15F), use 5W/gal or more.
Should I use one heater or two?
For tanks over 75 gallons, using two smaller heaters is recommended over one large heater. This provides redundancy (if one fails, the other prevents catastrophe), more even heat distribution, and reduces the risk of overheating from a stuck-on heater.
Where should I place the aquarium heater?
Place the heater near a filter intake or area of good water flow for even heat distribution. Submersible heaters should be positioned horizontally or at a 45-degree angle near the bottom. Always use a separate thermometer to verify temperature.
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