7 Reliable Heaters Fully Submersible with Thermostat

Try to live in Minnesota or anywhere in Canada without a heating system, and see how that goes.

I’m just trying to point out that you should also use the best aquarium heater you can get for your fish when they need it because the consequences can be fatal.

My recommended heater is the Fluval E, continue reading for more options.

Why Do You Need a Heater?

Types of Aquarium Heater - Where Should You Place It?

Best & Most Efficient Aquarium Heaters Reviews

So now let’s take a closer look at some of the most popular aquarium heaters you can buy today.


1. JBJ True Temp Titanium Heating System

The JBJ True Temp aquarium heating system consists of a True Temp digital controller, remote temperature-sensing probe and titanium heating element.

The True Temp controller has push-button controls and an LED display. A second LED light shows when the heating element is operating.

The controller’s internal memory saves the temperature setting, even during a power failure. Regular aquarium heaters have a thermostat inside the glass tube, near the heating element. This can lead to inaccurate temperature control and frequent on/off cycles.

The JBJ digital controller comes with a quick disconnect temperature probe with a 5-foot cable. You can place the probe just about anywhere in the aquarium. The probe and controller are rated at +/- 0.5 F accuracy. The digital controller has a temperature set point range between 32-99F.

The JBJ titanium heating element has no thermostat. It functions only as a heating element. Different wattage elements can be used with the controller. The heating element plugs into the external True Temp unit and is turned on and off automatically.

Another feature of the JBJ True Temp system is the option to calibrate the heater. Unlike factory-calibrated submersible heaters, the True Temp controller allows you to check and calibrate the heating system with a thermometer.

If the initial factory calibration is off a few degrees, you can correct it for more accurate temperature control.


  • Corrosion-proof titanium for saltwater and freshwater aquariums.
  • Comes with a heater guard to protect against fish burns and rock slides.
  • External temperature probe.
  • Ability to recalibrate if necessary.
  • Available in a variety of wattages.
  • Digital controller remembers settings and calibration.
  • Comes with in-tank mounting hardware.


  • More expensive that standard heaters.

2. Aquatop Analog Glass Submersible Heater

This heater measures 10 x 1.25 x 1.25 inches, for 150W of power.

This gives you a temperature range of 68° to 93° F for up to 40-gallon tanks.

Its warranty is only for a year, although you can check the producer's website if this changes—and it only applies when you buy from an authorized reseller.

It comes with suction cups for the setup, while it also features double insulation with high-quality insulated glass. You just turn a knob to adjust the temperature, and the display tells you the temperature setting.

Other power ranges are available, from 50W to 300W.​


  • It’s very powerful.
  • It’s easy to set up.
  • Its temperature settings are quite accurate.
  • It’s easy enough to adjust the temperature settings, and the display for the temperature setting is highly visible.
  • It’s quite hardy, with many other people saying that it has worked for them for years.
  • It’s very affordable.


  • Its warranty is only a year. Even though that’s a lot better than some pet stores offer (some of that offer only 15-day warranties) other companies offer a longer time frame.
  • It’s a bit fragile for shipping, with customers reporting that they received shattered heaters.

3. EHEIM Jager Aquarium Thermostat Heater

This fully submersible heater measures 1.4 x 19.9 inches, and it’s recommended that you place it vertically.

It’s available at different watts, from 50 watts all the way to 300 watts (there are 9 models available).

The 300 watts can handle as much as 150 gallons, although the recommended ratio is 5 watts per gallon of water.

The 25W is one of the best betta heaters around, as it can heat the water to at least 78° F in small tanks no bigger than 7 gallons.

The warranty is good for 3 years. The setup requires some calibration, however.


  • The TruTemp dial stays within 0.5 of your desired temperature.
  • It turns itself off when the water level goes low (hence the horizontal recommendation).
  • The glass is shatter-proof and shock-resistant.
  • It has a good reputation for durability.
  • You see an indicator light when it’s working.


  • It’s very long, and it may be difficult to set horizontally.

4. Aqueon Pro Heater

This is also another fully submersible heater that measures 4 x 14 x 2 inches.

It’s available in 5 different watts, and the 250W version can handle raising the temperature 15° F above room temperature in a 90-gallon tank.

It’s easy enough to install, but you’ll need to follow the directions in the setup guide.

The temperature is in Fahrenheit, and you’ll just need to set this horizontally so that you can see the temperature setting. There’s also an indicator light.

As for the warranty, there’s nothing better in the industry as you get a lifetime warrantee.


  • The lifetime warranty is truly excellent.
  • The warranty is also probably redundant, because it’s shatter-proof and virtually indestructible.
  • It contains an electronic thermostat so it’s accurate. These advantages combined have made it one of the top rated aquarium heaters today.


  • The customer service can be hit or miss—some get excellent service, while others not so much.

5. Fluval E Electronic Heater

This 300W heater is fully submersible, and it can handle 100 gallons with a temperature range of 68° to 93° F.

It’s actually available in 4 versions, with the 50W version good for up to 15 gallons.

It offers a great LCD display of the temperature, and it’s in both °C and °F.

It’s easy enough to set up in various angles, although the manual warns against setting this horizontally.

Just follow the directions, as there are steps involved.

It also comes with a 5-year warranty.


  • It offers accurate temperature settings with its dual temperature sensors. You can actually set the temperature in 0.5 degree increments.
  • It comes with an LCD display.
  • The fish guard is integrated, so that your fish doesn’t get in contact with the heating element. It’s even protected against shocks from bigger fish species.


  • Setting it up horizontally may void the warranty.
  • You’ll need to follow the steps in the guide when setting it up.

6. Finnex Hang-On Electronic Controller Heater (Titanium)

This 500-watt fully submersible heater only measures 14.5 x 1 x 1 inches.

It works very quickly and powerfully, as it’s capable of handling up to 120 gallons. Its temperature range is from 70 to 92° F.

The temperature control is set outside the water, which is nicely convenient.

It offers an accurate temperature setting (within 2 degrees) and there’s a LED heating indicator. It does warn that it should only be in a horizontal position, however.

It’s quite tough too, with its corrosion-resistant titanium tubes. This makes it ideal even for saltwater application. Unfortunately, the warranty situation is a bit on the murky side.

There is also a model that includes a heater guard, in case you need more protection for your fish​.

A deluxe version is available as well. It comes with an advanced controller and a memory chip to store settings in case of power outage. Be sure to check out the producer's website for more detailed info and features. The wattage of the deluxe model goes from 300W to 800W.


  • It can work very quickly with its titanium tube.
  • The control is outside the water.
  • It doesn’t take up much space in the tank.


  • It may be tough, but that warranty problem can be trouble.

7. Cobalt Aquatics Neo-Therm Heater

Now this fully submersible heater is small, as it only measures 11 x 1.5 x 0.5 inches.

The 150W it’s able to set the temperature from 66° to 96° F in a 40-gallon tank.

It has to be placed vertically, or you might void the 3-year warranty.

This offers very accurate temperature readings, with up to 0.5° F accuracy. The LED display even shows the set temp and the tank temp at the same time. It also shuts off automatically before it overheats, and the outer casing is shatterproof.

​Other wattage available are the 50W, 75W, 100W, 200W and 300W.


  • The temperature accuracy and display is terrific.
  • Its durability is fine.
  • It’s also easy to use with its “one touch” control system.



8. Hydor In-Line Aquarium heater

Maintaining a stable water temperature is essential for ensuring a healthy environment for fish, corals and other aquatic life.

Hydor In-Line External Heaters are designed to be installed in-line with an external canister filter.

Regular aquarium heaters need to be submerged inside the aquarium.

Water movement disperses the heated water throughout the tank.

There are several benefits to the Hydor in-line heating system. Mounting the heater outside of the aquarium saves space inside the tank. You’ll have more room for fish, inverts, live rock and plants. Big fish and tumbling live rock can break ordinary glass heaters.

An external heater eliminates all these problems. Just install the heater on the outflow of a canister filter.

The Hydor heater has hose barbs and tightening nuts to secure the heater onto the tubing. Setting and adjusting the heater is easy too. The temperature is set with a dial. A red LED indicates when the heater is operating. No more wet hands!

The Hydor In-Line External Heater uses a polymer PTC heating element. Positive temperature coefficient (PTC) heaters self-limit, meaning they will never get warmer than the pre-set level. This means the Hydro in-line heater can never over-heat and “fry” your aquarium.

The other benefit of the Hydor design is constant exposure to water movement. Because the heater is in a stream of flowing water from the canister filter, the aquarium is always bathed in heated water. This can help maintain a stable water temperature throughout the aquarium.


  • Can never over-heat the water.
  • External installation saves space in the tank.
  • Easy to make temperature adjustments.
  • Made of unbreakable plastic.
  • Provides pre-warmed water circulation.


  • Must be used with a canister filter.
  • Cannot be mounted horizontally.
  • Can’t see the indicator light if the heater is behind the aquarium.

My Pick

My personal favorite is the Fluval E Electronic Heater.

It comes with heater guards that also protect my fish, and it should be a boon for many beginners as well. They’ve had some quality issues in the past but recent aquarium heater reviews are mostly positive as long as it survives the delivery. The 5-year warranty is nice too, and it’s very easy to use.

All others are OK, especially the Cobalt for smaller aquariums.

Leave a Comment:

Erich Keser says

I have just had a second Fluval E behave erratically, after another, in another failed completely. Mu Eheim/Jager have generally proved much more reliable.

    Bob Flickerton says

    Hey Erich, thanks a lot for sharing your experience with us! Glad you finally found something suitable for your setup. Best, Bob.

Fish Keeper says

I bought a Fluval E heater based on this review and nowhere is any “auto shutoff” feature mentioned in the user manual or (later confirmed) on the website.

Contacting Fluval confirmed that this heater DOES NOT have that feature.

Anyone considering this heater for that feature (as I did) please do some research.
(Yeah, I know I should know better than trust anything anyone writes on the internet).

It is an OK heater but you need a good water flow around the unit or else the “LF” error.

Fish Keeper says

Hi Bob, The auto shutoff feature that was I was referring to was the “out of water shut off feature”. This is the feature Fluval confirmed to me is missing.

Some manufacturers claim auto shutoff if the water is too hot, which is stupid because that is what the heater is suppose to do anyway if the water is too hot.

I am going try the Cobalt heater on my next tank. Thanks for the info.

Brent Dow says

In your review you recommend the Eheim heater being placed horizontally. The manufacturer recommends vertical only.

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