How it works
A common mistake is buying a heater based only on tank size. The true determining factor is the temperature difference between your lowest room temperature (e.g., during winter nights) and your target water temperature. This calculator determines the minimum wattage required to bridge that gap safely.
Example
Scenario: You have a 100 Liter tank. You want the water at 26°C. Your house gets as cold as 18°C in winter.
- Volume: 100 Liters
- Temperature Difference: 26°C - 18°C = 8°C difference.
- Calculation: Since the difference is between 5°C and 10°C, the rule of thumb is ~1.5 watts per liter.
Verdict: You need approximately 150 Watts. The calculator will round this to standard heater sizes (e.g., 150W).
FAQ
Can I just buy a much larger heater to be safe?
No. An oversized heater can quickly boil your fish if the thermostat gets stuck in the 'ON' position. It's safer to buy a correctly sized heater, or run two smaller heaters (e.g., two 100W instead of one 200W) for redundancy.
Does using a lid affect the required wattage?
Yes, significantly. Open-top aquariums lose a lot of heat through evaporation. The calculator provides a safe baseline, but if you have a tight-fitting lid, your heater won't have to work as hard.