Heater size estimate
Use real water volume when possible. If you only know tank dimensions, calculate tank volume first, then come back here.
This is a planning estimate, not a safety guarantee. Always use an aquarium thermometer and avoid large sudden temperature changes.
How to choose aquarium heater wattage
Heater wattage is driven by the temperature rise your aquarium needs to maintain. A tank in a stable warm room needs less power than the same tank in a cold room, near a window, or with an open top. For larger aquariums, two heaters can improve heat distribution and add redundancy.
Aquarium heater FAQ
What size heater do I need for my aquarium?
It depends on real water volume and the difference between your coldest room temperature and target water temperature. Larger temperature gaps need more wattage.
Is one large heater or two smaller heaters better?
For larger tanks, two smaller heaters placed apart can heat more evenly and reduce the impact if one heater stops working.
Do planted aquariums need heaters?
Many tropical planted aquariums use heaters to keep fish, shrimp, and plants in a stable range. Cold-water setups may not need one.