Sized for a 40 gallon tank
| Model | Rated for | Power | Length |
|---|---|---|---|
| Aqueon Pro 100 Adjustable, electronic · Its 100 W is under both charts (Aqueon’s 150 W, Fluval’s 200 W), so it may not hold 78 °F unless the room stays warmer than 70 °F. | 15–40 gal | 100 W | 10.5 in |
| Aqueon Submersible Glass Heater 100 W Adjustable submersible · Its 100 W is under both charts (Aqueon’s 150 W, Fluval’s 200 W), so it may not hold 78 °F unless the room stays warmer than 70 °F. | Up to 40 gal | 100 W | 10.325 in |
| hygger Precise Aquarium Heater 200W Adjustable, electronic | 20–40 gal | 200 W | 9.25 in |
| hygger Titanium Tube Heater 200W Adjustable, electronic | 30–40 gal | 200 W | 10.63 in |
| Tetra HT40 Preset | 30–40 gal | 150 W | Not published |
| Fluval M150 Adjustable submersible | Up to 45 gal | 150 W | 13 in |
| EHEIM thermocontrol 125 Adjustable submersible · Its 125 W is under both charts (Aqueon’s 150 W, Fluval’s 200 W), so it may not hold 78 °F unless the room stays warmer than 70 °F. | 39.6–53 gal | 125 W | 12.6 in |
| Aqueon Pro 150 Adjustable, electronic | Up to 55 gal | 150 W | 12.75 in |
| Aqueon Submersible Glass Heater 150 W Adjustable submersible | Up to 55 gal | 150 W | 11.875 in |
| Aqueon Preset Heater 150 W Preset | Up to 55 gal | 150 W | Not published |
| Tetra HT55 Preset | 40–55 gal | 200 W | Not published |
| hygger Precise Aquarium Heater 300W Adjustable, electronic | 40–60 gal | 300 W | 9.25 in |
| Fluval E200 Adjustable, electronic | Up to 65 gal | 200 W | 14 in |
| Fluval M200 Adjustable submersible | Up to 65 gal | 200 W | 13 in |
| Aqueon Pro 200 Adjustable, electronic | Up to 75 gal | 200 W | 12.75 in |
| Aqueon Submersible Glass Heater 200 W Adjustable submersible | Up to 75 gal | 200 W | 13 in |
| Aqueon Preset Heater 200 W Preset | Up to 75 gal | 200 W | Not published |
| Fluval M300 Adjustable submersible | Up to 80 gal | 300 W | 15 in |
| Aqueon Pro 300 Adjustable, electronic | Up to 100 gal | 300 W | 15 in |
| Aqueon Submersible Glass Heater 300 W Adjustable submersible | Up to 100 gal | 300 W | 15.25 in |
| Fluval E300 Adjustable, electronic | Up to 100 gal | 300 W | 14 in |
The charts are for an average room. In a colder room, or a tank without a lid, work out your own figure in the heater size calculator; for a warmer one, the smaller heaters here are enough.
Not for a 40 gallon tank
- hygger Digital Mini Heater 15W: Rated 0.4–2.64 gal: too small for 40 gallons.
- Aqueon Aquatic Flat Heater 7.5 W: Rated 1–3 gal: too small for 40 gallons.
- hygger Digital Mini Heater 25W: Rated 0.4–5.3 gal: too small for 40 gallons.
- EHEIM thermocontrol 25: Rated 5.2–6.6 gal: too small for 40 gallons.
- Aqueon Aquatic Flat Heater 15 W: Rated 5–10 gal: too small for 40 gallons.
- hygger Precise Aquarium Heater 50W: Rated 5–10 gal: too small for 40 gallons.
- Tetra HT10: Rated 2–10 gal: too small for 40 gallons.
- hygger Digital Mini Heater 50W: Rated 0.4–11.9 gal: too small for 40 gallons.
- Fluval M50: Rated up to 15 gal: too small for 40 gallons.
- hygger Titanium Tube Heater 50W: Rated 10–15 gal: too small for 40 gallons.
- EHEIM thermocontrol 50: Rated 6.6–15.8 gal: too small for 40 gallons.
- hygger Digital Mini Heater 75W: Rated 0.4–15.9 gal: too small for 40 gallons.
- Aqueon Pro 50: Rated up to 20 gal: too small for 40 gallons.
- Aqueon Submersible Glass Heater 50 W: Rated up to 20 gal: too small for 40 gallons.
- hygger Precise Aquarium Heater 100W: Rated 10–20 gal: too small for 40 gallons.
- hygger Titanium Tube Heater 100W: Rated 15–20 gal: too small for 40 gallons.
- Aqueon Preset Heater 50 W: Rated up to 20 gal: too small for 40 gallons.
- EHEIM thermocontrol 75: Rated 15.8–26.4 gal: too small for 40 gallons.
- Cobalt Aquatics Neo-Therm Pro 100W: Rated up to 29 gal: too small for 40 gallons.
- Fluval E100: Rated up to 30 gal: too small for 40 gallons.
- Fluval M100: Rated up to 30 gal: too small for 40 gallons.
- Aqueon Preset Heater 100 W: Rated up to 30 gal: too small for 40 gallons.
- Tetra HT30: Rated 10–30 gal: too small for 40 gallons.
- EHEIM thermocontrol 100: Rated 26.4–39.6 gal: too small for 40 gallons.
- hygger Titanium Tube Heater 300W: Rated 50–60 gal: built for bigger tanks than 40 gallons.
- EHEIM thermocontrol 150: Rated 53–79 gal: built for bigger tanks than 40 gallons.
- hygger Titanium Tube Heater 500W: Rated 70–80 gal: built for bigger tanks than 40 gallons.
- hygger Precise Aquarium Heater 500W: Rated 55–100 gal: built for bigger tanks than 40 gallons.
- EHEIM thermocontrol 200: Rated 79–106 gal: built for bigger tanks than 40 gallons.
- EHEIM thermocontrol 250: Rated 106–159 gal: built for bigger tanks than 40 gallons.
- EHEIM thermocontrol 300: Rated 159–264 gal: built for bigger tanks than 40 gallons.
Before you choose
Put the heater where the filter’s flow passes it, so the warmth spreads, and check the temperature with a separate thermometer. How to size and place a heater.
Tank pages: 40 gallon breeder · Filters for a 40 gallon tank →