Tip: Two smaller heaters are often safer than one large one (redundancy).
Based on temperature potential difference and volume.
About this calculator
Heater Selection Guide
Maintaining a stable temperature is vital for aquatic life. The power required depends on the volume of water and the 'Delta T' (ΔT) - the difference between the coldest room temperature and your target water temperature. A general rule is 3-5 watts per gallon, but efficient modern heaters may require less.
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Pro Tips
Reliability: Aquarium heaters have a high failure rate. Replace them every 1-2 years or use an external inkbird-style temperature controller.
Placement: Place heaters near filter outflows. This ensures heated water is quickly distributed throughout the tank.
Calibration: Heater dials are notoriously inaccurate. Always verify with a separate thermometer.
Cold Rooms: If your room drops below 18°C at night, consider insulating the back and sides of the tank to save energy.
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Fun Facts
"Water has a high 'specific heat capacity' (4.184 J/g°C), meaning it takes 4x more energy to heat water than air!"
"Fish are poikilothermic (cold-blooded), so their metabolism speeds up in warmer water and slows down in cooler water."
"Goldfish are comfortable at 20°C, while Discus fish need a toasty 28-30°C."
"A lid on your aquarium can reduce heat loss (and evaporation) by over 50%."
