Aquarium Heater Calculator
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Quick Wattage Guide
Standard rule: 3-5 watts per gallon, more for colder rooms
Top Rated Aquarium Heaters
Fluval E-Series
LCD temp display, dual sensors, fish guard included. Most accurate heater available.
Eheim Jager
German engineering, precise thermostat, shatter-proof glass. Industry standard for decades.
Aqueon Pro
Lifetime warranty, shatter-resistant, LED indicator. Great bang for buck.
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Heater Sizing Guide
Why Proper Sizing Matters
An undersized heater will struggle to maintain temperature, especially in cold weather. This causes stress and makes fish susceptible to disease. An oversized heater wastes energy and can overheat the tank if the thermostat fails.
The Dual Heater Strategy
For tanks over 40 gallons, we recommend using two heaters at 50-75% of the total needed wattage each. Benefits: if one fails "on," the other won't overheat the tank; if one fails "off," the other maintains temp; more even heat distribution in larger tanks.
Placement Tips
- Place near filter intake or powerhead for water circulation
- Horizontal placement heats more evenly than vertical
- Never let the heater run while exposed to air
- Wait 30 minutes after installing before plugging in
Signs of Heater Problems
- Temperature swings of more than 2°F
- Heater light always on or never on
- Fish gasping at surface (overheating)
- Fish inactive, not eating (too cold)