Aquarium heating reference tool
Aquarium Heater Size Calculator: Tank Volume & Temperature Delta
Calculate the room-to-target temperature delta, then check whether your water volume and room conditions match a row in Aqueon's current heater guide. The tool reports a manufacturer-table wattage only when the published conditions apply.
This calculator does not use a universal watts-per-gallon formula. Aqueon's table is manufacturer-specific, and the same wattage does not make heaters interchangeable across brands or product families.
Manufacturer-chart lookup
Calculate temperature delta and check the current Aqueon heater table
Enter practical water volume plus the coldest normal room temperature and target water temperature. A wattage result appears only when the inputs fit Aqueon's current published table conditions.
Enter your conditions, then select Check heater chart.
Current Aqueon heater sizing chart
Manufacturer source rechecked September 30, 2026. Aqueon publishes the chart below for a standard room-temperature basis of 68–72°F. The calculator above uses this same dataset; the table is shown here so the manufacturer rows remain visible even without JavaScript.
| Aquarium size | 5°F rise | 10°F rise | 15°F rise |
|---|---|---|---|
| 5 gallon | 1 × 50W | 1 × 50W | 1 × 50W |
| 10 gallon | 1 × 50W | 1 × 50W | 1 × 50W |
| 20 gallon | 1 × 50W | 1 × 100W | 1 × 100W |
| 30 gallon | 1 × 100W | 1 × 100W | 1 × 150W |
| 55 gallon | 1 × 150W | 1 × 150W | 1 × 200W |
| 75 gallon | 1 × 200W | 1 × 200W | 1 × 300W |
| 100 gallon | 1 × 300W | 1 × 300W | 1 × 300W |
| 120/125 gallon | 2 × 200W | 2 × 200W | 2 × 200W |
| 150–210 gallon | 2 × 300W | 2 × 300W | 2 × 300W |
The chart is descriptive manufacturer data, not a universal watts-per-gallon rule. For example, Aqueon publishes two-heater configurations for the 120/125-gallon and 150–210-gallon rows; PetGearReport preserves those configurations instead of converting them into a single-element recommendation.
What the Aqueon lookup covers
Aqueon's current heater guide is based on a standard room temperature of 68–72°F and publishes columns for temperature rises of 5°F, 10°F and 15°F. The current web table contains rows for 5, 10, 20, 30, 55, 75 and 100 gallons, a 120/125-gallon row, and a 150–210-gallon range.
When your required rise falls between the published columns, this tool uses the next higher published Aqueon band. That is a conservative PetGearReport lookup choice; it does not create a new manufacturer wattage claim. If room temperature falls outside 68–72°F, the rise exceeds 15°F, or the aquarium volume has no current row, the calculator deliberately returns no wattage.
Source: Aqueon — Setting Up a Freshwater Aquarium / Heater Guide. Current web guidance was rechecked September 30, 2026. Older Aqueon PDF/chart assets contain some different historical rows, so they are not used as this calculator's dataset.
Why the result is not a cross-brand prescription
Manufacturers define heater capacity differently. Fluval's current T-Series guidance says additional heating capacity is likely necessary when ambient room temperature is more than 10°F / 6°C below the set temperature, while the current M-Series guidance uses 18°F / 10°C. Those family-specific thresholds show why a wattage number should not be detached from the exact product's documentation.
Use the aquarium heater size guide for the full sizing method, then compare current products in the best aquarium heaters guide. For independent verification after installation, see the aquarium thermometer guide.
Start with practical water volume
Retail tank capacity can differ from the water actually being heated because of fill level, substrate, rock, wood and internal equipment. If you do not know practical water volume, use the aquarium volume calculator first. The heater lookup then uses that value only as an input to a published manufacturer row; it does not convert volume into a generic wattage formula.
For partially filled aquatic-turtle habitats, use the turtle tank heater guide as well. Turtle systems add actual-water-volume, animal-contact, basking-heat and UVB considerations that a generic aquarium wattage table cannot decide.
How to use a wattage result safely
A matched Aqueon row is a starting reference for Aqueon-style heater selection under the published room-temperature basis. It does not verify physical fit, thermostat architecture, allowed orientation, water circulation, redundancy strategy or livestock temperature requirements.
After choosing an exact model, follow its current installation instructions and verify the aquarium with an independent thermometer away from the heating element or control probe. If the calculator returns no wattage, that is intentional: use exact model guidance instead of interpolation.
Primary sources
- Aqueon Heater Guide — current 68–72°F basis and 5°F/10°F/15°F sizing table.
- Fluval T-Series FAQ — current 10°F / 6°C ambient-to-set additional-capacity guidance.
- Fluval M200 / M-Series guidance — current 18°F / 10°C ambient-to-set additional-capacity guidance.