Heaters · Adjustable, electronic
Fluval E100
Rated for a 20 gal tank
- Manufacturer rating
- Up to 30 US gal
- Power
- 100 W
Consider: The body is 11.75 inches tall. Check the available mounting space and water depth before choosing it for a shallow tank.
Fish tank heater: compare the choices
52 heaters, drawn at their published size on your tank and checked against the maker’s rating.
52 models
Fit marked for 20 gallon long (example)
Heaters · Adjustable, electronic
Fluval E200
Rated for a 20 gal tank
- Manufacturer rating
- Up to 65 US gal
- Power
- 200 W
Consider: The 14-inch body can exclude shallow tanks. Compare that height with the mounting position and water depth in the instructions before ordering.
Heaters · Adjustable, electronic
Aqueon Pro 50
Rated for a 20 gal tank
- Manufacturer rating
- Up to 20 US gal
- Power
- 50 W
Consider: A cold room can demand more heat than the gallon rating suggests. Compare your coolest room temperature and target water temperature with the manufacturer’s sizing chart.
Heaters · Adjustable, electronic
Aqueon Pro 100
Rated for a 20 gal tank
- Manufacturer rating
- 15–40 US gal
- Power
- 100 W
Consider: A cold room can demand more heat than the gallon rating suggests. Compare your coolest room temperature and target water temperature with the manufacturer’s sizing chart.
Heaters · Adjustable, electronic
Aqueon Pro 150
Rated for a 20 gal tank
- Manufacturer rating
- Up to 55 US gal
- Power
- 150 W
Consider: A cold room can demand more heat than the gallon rating suggests. Compare your coolest room temperature and target water temperature with the manufacturer’s sizing chart.
Heaters · Adjustable, electronic
Aqueon Pro 200
Rated for a 20 gal tank
- Manufacturer rating
- Up to 75 US gal
- Power
- 200 W
Consider: A cold room can demand more heat than the gallon rating suggests. Compare your coolest room temperature and target water temperature with the manufacturer’s sizing chart.
Heaters · Adjustable, electronic
Aqueon Pro 300
Rated for a 20 gal tank
- Manufacturer rating
- Up to 100 US gal
- Power
- 300 W
Consider: A cold room can demand more heat than the gallon rating suggests. Compare your coolest room temperature and target water temperature with the manufacturer’s sizing chart.
Heaters · Preset
Aqueon Preset Heater 50 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 20 US gal
- Power
- 50 W
Consider: Preset to 78 °F with nothing to set: right for most tropical fish, too warm for goldfish and other cool-water fish. Choose an adjustable heater if yours need a different temperature.
Heaters · Preset
Aqueon Preset Heater 100 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 30 US gal
- Power
- 100 W
Consider: Preset to 78 °F with nothing to set: right for most tropical fish, too warm for goldfish and other cool-water fish. Choose an adjustable heater if yours need a different temperature.
Heaters · Preset
Aqueon Preset Heater 150 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 55 US gal
- Power
- 150 W
Consider: Preset to 78 °F with nothing to set: right for most tropical fish, too warm for goldfish and other cool-water fish. Choose an adjustable heater if yours need a different temperature.
Heaters · Preset
Aqueon Preset Heater 200 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 75 US gal
- Power
- 200 W
Consider: Preset to 78 °F with nothing to set: right for most tropical fish, too warm for goldfish and other cool-water fish. Choose an adjustable heater if yours need a different temperature.
Heaters · Adjustable submersible
Aqueon Submersible Glass Heater 50 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 20 US gal
- Power
- 50 W
Consider: Set it anywhere from 68 to 88 °F, a degree at a time. At 8.75 in long, check it fits upright below your water line, or lay it on its side.
Heaters · Adjustable submersible
Aqueon Submersible Glass Heater 100 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 40 US gal
- Power
- 100 W
Consider: Set it anywhere from 68 to 88 °F, a degree at a time. At 10.325 in long, check it fits upright below your water line, or lay it on its side.
Heaters · Adjustable submersible
Aqueon Submersible Glass Heater 150 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 55 US gal
- Power
- 150 W
Consider: Set it anywhere from 68 to 88 °F, a degree at a time. At 11.875 in long, check it fits upright below your water line, or lay it on its side.
Heaters · Adjustable submersible
Aqueon Submersible Glass Heater 200 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 75 US gal
- Power
- 200 W
Consider: Set it anywhere from 68 to 88 °F, a degree at a time. At 13 in long, check it fits upright below your water line, or lay it on its side.
Heaters · Adjustable submersible
Aqueon Submersible Glass Heater 300 W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 100 US gal
- Power
- 300 W
Consider: Set it anywhere from 68 to 88 °F, a degree at a time. At 15.25 in long, check it fits upright below your water line, or lay it on its side.
Heaters · Preset
Tetra HT30
Rated for a 20 gal tank
- Manufacturer rating
- 10–30 US gal
- Power
- 100 W
Consider: Preset to 78°F with no user adjustment. Choose an adjustable heater if your fish need a different temperature.
Heaters · Adjustable, electronic
Cobalt Aquatics Neo-Therm Pro 100W
Rated for a 20 gal tank
- Manufacturer rating
- Up to 29 US gal
- Power
- 100 W
Consider: Its published rating stops at 29 gallons. For a larger tank, use the manufacturer’s sizing guidance instead of assuming this single 100W unit is enough.
Heaters · Adjustable submersible
Fluval M100
Rated for a 20 gal tank
- Manufacturer rating
- Up to 30 US gal
- Power
- 100 W
Consider: A cold room or open tank changes the heating load. Use the exact-model sizing chart with your coolest room temperature before choosing from the gallon rating alone.
Heaters · Adjustable submersible
Fluval M150
Rated for a 20 gal tank
- Manufacturer rating
- Up to 45 US gal
- Power
- 150 W
Consider: A cold room or open tank changes the heating load. Use the exact-model sizing chart with your coolest room temperature before choosing from the gallon rating alone.
Heaters · Adjustable submersible
Fluval M200
Rated for a 20 gal tank
- Manufacturer rating
- Up to 65 US gal
- Power
- 200 W
Consider: A cold room or open tank changes the heating load. Use the exact-model sizing chart with your coolest room temperature before choosing from the gallon rating alone.
Heaters · Adjustable submersible
Fluval M300
Rated for a 20 gal tank
- Manufacturer rating
- Up to 80 US gal
- Power
- 300 W
Consider: At 15 inches it is the longest M heater. Check it fits your water depth at the angle you mount it, and size for your coolest room, not the gallon rating alone.
Heaters · Adjustable, electronic
Fluval E300
Rated for a 20 gal tank
- Manufacturer rating
- Up to 100 US gal
- Power
- 300 W
Consider: The 14-inch body can exclude shallow tanks. Compare that height with the mounting position and water depth in the instructions before ordering.
Heaters · Adjustable submersible
EHEIM thermocontrol 75
Rated for a 20 gal tank
- Manufacturer rating
- 15.8–26.4 US gal
- Power
- 75 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable, electronic
hygger Precise Aquarium Heater 100W
Rated for a 20 gal tank
- Manufacturer rating
- 10–20 US gal
- Power
- 100 W
Consider: The controller stays dry outside the tank and remembers your setting through a power cut, but the glass tube has no guard around it.
Heaters · Adjustable, electronic
hygger Precise Aquarium Heater 200W
Rated for a 20 gal tank
- Manufacturer rating
- 20–40 US gal
- Power
- 200 W
Consider: The controller stays dry outside the tank and remembers your setting through a power cut, but the glass tube has no guard around it.
Heaters · Adjustable, electronic
hygger Titanium Tube Heater 100W
Rated for a 20 gal tank
- Manufacturer rating
- 15–20 US gal
- Power
- 100 W
Consider: Titanium won’t shatter like glass, and the controller remembers your setting through a power cut, but the heater and its sensor are two pieces to place in the tank.
Heaters · Flat
Aqueon Aquatic Flat Heater 7.5 W
Rated 1–3 gal, not 20 gal
- Manufacturer rating
- 1–3 US gal
- Power
- 7.5 W
Consider: Small and flat, with no temperature to set: it adds up to 6 °F to the room, so a 78 °F tank needs a room of 72 °F or warmer, day and night.
Heaters · Flat
Aqueon Aquatic Flat Heater 15 W
Rated 5–10 gal, not 20 gal
- Manufacturer rating
- 5–10 US gal
- Power
- 15 W
Consider: Small and flat, with no temperature to set: it adds up to 6 °F to the room, so a 78 °F tank needs a room of 72 °F or warmer, day and night.
Heaters · Preset
Tetra HT10
Rated 2–10 gal, not 20 gal
- Manufacturer rating
- 2–10 US gal
- Power
- 50 W
Consider: Preset to 78°F with no user adjustment. Choose an adjustable heater if your fish need a different temperature.
Heaters · Adjustable submersible
Fluval M50
Rated up to 15 gal, not 20 gal
- Manufacturer rating
- Up to 15 US gal
- Power
- 50 W
Consider: A cold room or open tank changes the heating load. Use the exact-model sizing chart with your coolest room temperature before choosing from the gallon rating alone.
Heaters · Preset
Tetra HT40
Rated 30–40 gal, not 20 gal
- Manufacturer rating
- 30–40 US gal
- Power
- 150 W
Consider: Preset to 78°F with no user adjustment. Choose an adjustable heater if your fish need a different temperature.
Heaters · Preset
Tetra HT55
Rated 40–55 gal, not 20 gal
- Manufacturer rating
- 40–55 US gal
- Power
- 200 W
Consider: Preset to 78°F with no user adjustment. Choose an adjustable heater if your fish need a different temperature.
Heaters · Adjustable submersible
EHEIM thermocontrol 25
Rated 5.2–6.6 gal, not 20 gal
- Manufacturer rating
- 5.2–6.6 US gal
- Power
- 25 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable submersible
EHEIM thermocontrol 50
Rated 6.6–15.8 gal, not 20 gal
- Manufacturer rating
- 6.6–15.8 US gal
- Power
- 50 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable submersible
EHEIM thermocontrol 100
Rated 26.4–39.6 gal, not 20 gal
- Manufacturer rating
- 26.4–39.6 US gal
- Power
- 100 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable submersible
EHEIM thermocontrol 125
Rated 39.6–53 gal, not 20 gal
- Manufacturer rating
- 39.6–53 US gal
- Power
- 125 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable submersible
EHEIM thermocontrol 150
Rated 53–79 gal, not 20 gal
- Manufacturer rating
- 53–79 US gal
- Power
- 150 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable submersible
EHEIM thermocontrol 200
Rated 79–106 gal, not 20 gal
- Manufacturer rating
- 79–106 US gal
- Power
- 200 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable submersible
EHEIM thermocontrol 250
Rated 106–159 gal, not 20 gal
- Manufacturer rating
- 106–159 US gal
- Power
- 250 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable submersible
EHEIM thermocontrol 300
Rated 159–264 gal, not 20 gal
- Manufacturer rating
- 159–264 US gal
- Power
- 300 W
Consider: There is no display: you set it on a dial, check the water with a thermometer and recalibrate the dial if the two disagree.
Heaters · Adjustable, electronic
hygger Digital Mini Heater 15W
Rated 0.4–2.64 gal, not 20 gal
- Manufacturer rating
- 0.4–2.64 US gal
- Power
- 15 W
Consider: Made for small tanks: it mounts upright or lying flat, even in the back chamber of an all-in-one tank, and the controller on its cord shows the water temperature.
Heaters · Adjustable, electronic
hygger Digital Mini Heater 25W
Rated 0.4–5.3 gal, not 20 gal
- Manufacturer rating
- 0.4–5.3 US gal
- Power
- 25 W
Consider: Made for small tanks: it mounts upright or lying flat, even in the back chamber of an all-in-one tank, and the controller on its cord shows the water temperature.
Heaters · Adjustable, electronic
hygger Digital Mini Heater 50W
Rated 0.4–11.9 gal, not 20 gal
- Manufacturer rating
- 0.4–11.9 US gal
- Power
- 50 W
Consider: Made for small tanks: it mounts upright or lying flat, even in the back chamber of an all-in-one tank, and the controller on its cord shows the water temperature.
Heaters · Adjustable, electronic
hygger Digital Mini Heater 75W
Rated 0.4–15.9 gal, not 20 gal
- Manufacturer rating
- 0.4–15.9 US gal
- Power
- 75 W
Consider: Made for small tanks: it mounts upright or lying flat, even in the back chamber of an all-in-one tank, and the controller on its cord shows the water temperature.
Heaters · Adjustable, electronic
hygger Precise Aquarium Heater 50W
Rated 5–10 gal, not 20 gal
- Manufacturer rating
- 5–10 US gal
- Power
- 50 W
Consider: The controller stays dry outside the tank and remembers your setting through a power cut, but the glass tube has no guard around it.
Heaters · Adjustable, electronic
hygger Precise Aquarium Heater 300W
Rated 40–60 gal, not 20 gal
- Manufacturer rating
- 40–60 US gal
- Power
- 300 W
Consider: The controller stays dry outside the tank and remembers your setting through a power cut, but the glass tube has no guard around it.
Heaters · Adjustable, electronic
hygger Precise Aquarium Heater 500W
Rated 55–100 gal, not 20 gal
- Manufacturer rating
- 55–100 US gal
- Power
- 500 W
Consider: The controller stays dry outside the tank and remembers your setting through a power cut, but the glass tube has no guard around it.
Heaters · Adjustable, electronic
hygger Titanium Tube Heater 50W
Rated 10–15 gal, not 20 gal
- Manufacturer rating
- 10–15 US gal
- Power
- 50 W
Consider: Titanium won’t shatter like glass, and the controller remembers your setting through a power cut, but the heater and its sensor are two pieces to place in the tank.
Heaters · Adjustable, electronic
hygger Titanium Tube Heater 200W
Rated 30–40 gal, not 20 gal
- Manufacturer rating
- 30–40 US gal
- Power
- 200 W
Consider: Titanium won’t shatter like glass, and the controller remembers your setting through a power cut, but the heater and its sensor are two pieces to place in the tank.
Heaters · Adjustable, electronic
hygger Titanium Tube Heater 300W
Rated 50–60 gal, not 20 gal
- Manufacturer rating
- 50–60 US gal
- Power
- 300 W
Consider: Titanium won’t shatter like glass, and the controller remembers your setting through a power cut, but the heater and its sensor are two pieces to place in the tank.
Heaters · Adjustable, electronic
hygger Titanium Tube Heater 500W
Rated 70–80 gal, not 20 gal
- Manufacturer rating
- 70–80 US gal
- Power
- 500 W
Consider: Titanium won’t shatter like glass, and the controller remembers your setting through a power cut, but the heater and its sensor are two pieces to place in the tank.
No models match these filters.
Clear the search or choose another tank size. The size filter only shows filters and heaters that their maker rates for that size.
The size filter and the fit marks use each maker’s tank-size rating for filters and heaters and the fixture span for lights. Drawings use the makers’ published sizes; positions are approximate. Where a maker doesn’t publish a rating, we don’t guess one; each model page says what is missing.
Before choosing heaters
Start with the coolest room temperature and the intended water temperature, then use that brand’s sizing chart. Check physical length, submersion and controls before choosing watts. A preset heater only makes sense if its fixed temperature suits your fish.
Check these against your tank in the equipment planner. Replaced and renamed models.
Every size by maker: API · Aquarium Co-Op · Aqueon · EHEIM · Fluval · Marineland · Seachem · Tetra · hygger
What to check before choosing heaters
By tank size: 5 gallon · 10 gallon · 20 gallon · 29 gallon · 40 gallon · 55 gallon · 75 gallon