9 Best Aquarium Heaters: Submersible, Immersible, In-line

Best Aquarium Heater

Aquariums are usually filled with water at room temperature but some fish, especially the tropical species, thrive well in warm waters. This is where an aquarium heater comes in.

Additionally, the water is not guaranteed to stay at a constant temperature because the heat outside might drop. Just like humans, fish do not like these frequent temperature changes and this further emphasizes the importance of an aquarium heater.

With this in mind, it is vital that you get the best aquarium heater. This article takes a close look at 10 of the best ones in the market so as to help you pick the most suitable one for your fish.

IMAGE

​PRODUCT

​FEATURES

Fluval A772

1. Fluval A772 (Best Overall Aquarium Heater)

  • Electronic heater with a color-coded LCD screen
  • 2 temperature sensors
  • Fish guard
  • 100-watt rating; ideal for up to 30-gallon tanks
Cobalt Aquatics 31004

2. Cobalt Aquatics 31004 (Electronic Aquarium Heater with Thermal Protection)

  • Electronic thermometer with +/– 0.5ºF accuracy
  • Thermal protection
  • Fully submersible with a thin profile design
  • 100-watt rating; ideal for up to 29-gallon tanks
Aqueon Pro

3. Aqueon Pro (Shatterproof Aquarium Heater)

  • Shatterproof, nearly indestructible outer shell
  • Adjustable settings; 68ºF to 88ºF heating range
  • Auto shut-off safety
  • LED heating indicator
Aquatop GH-50W

4. Aquatop GH-50W (Fully Submersible Aquarium Heater)

  • Fully submersible and includes suction cups
  • 68ºF to 93ºF temperature range
  • Double glass layer construction
  • 50-watt rating; ideal for up to 13-gallon tanks
Eheim 3612090

5. Eheim 3612090 (Aquarium Heater with Re-calibration Settings)

  • Recalibration settings for improved accuracy
  • Thermo safety control
  • Shock resistant and shatterproof glass construction
  • 50-watt rating; ideal for up to 16-gallon tanks
ViaAqua VA 50Q

6. ViaAqua VA 50Q (Aquarium Heater with a Ceramic Core)

  • Ceramic core distributes heat evenly
  • 68ºF to 93ºF temperature range
  • Visible temperature adjustment
  • 50-watt rating; ideal for up to 13-gallon tanks
Penn Plax CH8100

7. Penn Plax CH8100 (Affordable Aquarium Heater)

  • Affordable
  • Fully submersible in a vertical or horizontal orientation
  • 100-watt rating; ideal for up to 20-gallon tanks
  • Celsius and Fahrenheit scales
Lifegard Aquatics Aquarium Heater

8. Lifegard Aquatics Aquarium Heater (Best Aquarium Heater for Large Tanks)

  • 300-watt power rating; ideal for 110 – 150-gallon tanks
  • Suitable for fresh and saltwater aquariums
  • Thermal safety protection
  • Reinforced quartz glass construction
Hydor T08203

9. Hydor T08203 (In-Line Aquarium Heater)

  • In-line heater; does not consume space in the tank
  • High precision electronic temperature control
  • 65 – 93ºF temperature range
  • 300-watt rating; ideal for 53 – 80-gallon tanks

PRODUCT

1. Fluval A772

(Best Overall Aquarium Heater)

Fluval A772
  • Electronic heater with a color-coded LCD screen
  • 2 temperature sensors
  • Fish guard
  • 100-watt rating; ideal for up to 30-gallon tanks

2. Cobalt Aquatics 31004

(Electronic Aquarium Heater with Thermal Protection)

Cobalt Aquatics 31004
  • Electronic thermometer with +/– 0.5ºF accuracy
  • Thermal protection
  • Fully submersible with a thin profile design
  • 100-watt rating; ideal for up to 29-gallon tanks

3. Aqueon Pro

(Shatterproof Aquarium Heater)

Aqueon Pro
  • Shatterproof, nearly indestructible outer shell
  • Adjustable settings; 68ºF to 88ºF heating range
  • Auto shut-off safety
  • LED heating indicator

4. Aquatop GH-50W

(Fully Submersible Aquarium Heater)

Aquatop GH-50W
  • Fully submersible and includes suction cups
  • 68ºF to 93ºF temperature range
  • Double glass layer construction
  • 50-watt rating; ideal for up to 13-gallon tanks

5. Eheim 3612090

(Aquarium Heater with Re-calibration Settings)

Eheim 3612090
  • Recalibration settings for improved accuracy
  • Thermo safety control
  • Shock resistant and shatterproof glass construction
  • 50-watt rating; ideal for up to 16-gallon tanks

6. ViaAqua VA 50Q

(Aquarium Heater with a Ceramic Core)

ViaAqua VA 50Q
  • Ceramic core distributes heat evenly
  • 68ºF to 93ºF temperature range
  • Visible temperature adjustment
  • 50-watt rating; ideal for up to 13-gallon tanks

7. Penn Plax CH8100

(Affordable Aquarium Heater)

Penn Plax CH8100
  • Affordable
  • Fully submersible in a vertical or horizontal orientation
  • 100-watt rating; ideal for up to 20-gallon tanks
  • Celsius and Fahrenheit scales

8. Lifegard Aquatics Aquarium Heater

(Best Aquarium Heater for Large Tanks)

Lifegard Aquatics Aquarium Heater
  • 300-watt power rating; ideal for 110 – 150-gallon tanks
  • Suitable for fresh and saltwater aquariums
  • Thermal safety protection
  • Reinforced quartz glass construction

9. Hydor T08203

(In-Line Aquarium Heater)

Hydor T08203
  • In-line heater; does not consume space in the tank
  • High precision electronic temperature control
  • 65 – 93ºF temperature range
  • 300-watt rating; ideal for 53 – 80-gallon tanks

1. Fluval A772 – Best Overall Aquarium Heater

Fluval E Electronic Aquarium Heater
  • Power: 100 Watts
  • Ideal tank size: Up to 30 gallons

Fluval is one of the best aquarium heater brands in the market and this particular model does not disappoint. Although a bit expensive, the product has a very impressive array of features.  

For starters, it has an LCD screen that displays the set water temperature in both degrees Celsius and Fahrenheit. This makes it very easy to adjust because the results are displayed digitally on-screen.

Additionally, it has an easy-to-use adjustment lever for setting the temperature, and it does so in 0.5ºF increments or decrements.

The screen itself is also a safety feature because it lights up in green when the water is at the set temperature, blue when it is more than 2ºF below and red when it exceeds by more than 2ºF. This makes it the most reliable aquarium heater.

Dual temperature sensors make this possible by sensing the current water temperature in real time and displaying the results on the screen using those colors.

For safety, the heater has a fish guard, which is basically a protection layer that keeps the animals inside the aquarium from coming into direct contact with the heater core. This also protects the core from external shocks caused by large fish collisions.  

On the downside, this unit does not have a dry run protection feature and thus, might get destroyed when left on in an empty tank. 

Pros:

  • LCD screen with ºC and ºF output
  • Dual temperature sensors ​
  • Color-coded display
  • Easy-to-use adjustment lever
  • Protective fish guard ​

Cons:

  • Relatively expensive
  • ​No dry run protection

2. Cobalt Aquatics 31004 – Electronic Aquarium Heater with Thermal Protection

Cobalt Aquatics Neo-Therm Aquarium Heater
  • Power: 100 Watts
  • Ideal tank size: 29 gallons

Cobalt Aquatics’ 31004 features a fully electronic thermometer and thermostat, which are computer tested and proven to maintain the accurate temperature to + or – 0.5ºF. 

The whole system is guarded by a built-in thermal protection circuitry, which powers off the heater once it starts to overheat. This ensures you do not boil your fish and plants.

Additionally, this system includes an LED light that displays both the set temperature and the current tank temperature to enable you to monitor the temperature changes easily without using an external thermometer.

The product’s temperature settings range from 66ºF - 96ºF, and this basically covers all the required temperatures for most fish. As a result, the Neo-Therm is ideal for freshwater, saltwater, reef and terrarium tanks, which makes it a very versatile tool.

Other than that, the heater is fully submersible aquarium and has a thin profile (1/3 inch thick), which gives it a very modern look. This thin body is made from shatterproof material, making it virtually indestructible.

Other features include a reversible vertical mounting bracket with a suction cup and an easy to set, 1-touch system. The only problem is its high cost.  

Pros:

  • Fully electronic and accurate thermostat and thermometer.
  • Integrated thermal protection circuitry
  • Slim profile design
  • LED ​temperature indication
  • Ideal for saltwater, freshwater, reef and terrarium tanks

Cons:

  • Relatively expensive.
  • Designed for vertical hanging only

3. Aqueon Pro – Shatterproof Aquarium Heater

Aqueon Pro Adjustable Aquarium Heater
  • Power: 50 Watts
  • Ideal tank size: 10 gallons

This Aqueon Pro heater has a high-quality shell, which is shatterproof, non-corrosive and gives an even heat distribution across its length.

For temperature settings, the unit features a pointed control knob that can be used to adjust the heat to any value between 68ºF to 88ºF. Although this range is not as big as that of the Neo-Therm above, it still gives you some room to play with.

A built-in thermostat ensures that temperatures are kept steady and is accurate to + or – 1ºF. In case this fails, an auto shut-off mechanism kicks to ensure that you don’t kill your fish and resets once the water has cooled down.

LED lighting is used to indicate whether the heater is heating or not. It lights red when heating and green when not heating, and this makes it possible to monitor the unit from outside because this can also show you whether the unit is still functioning or not.

If the 50-watt model is too small for your tank, there are larger 100-watt model. However, despite the power size, all of them are fully submersible and can be positioned either vertically or horizontally.

Pros:

  • Shatterproof, non-corrosive shell
  • Adjustable temperature settings.
  • Auto shut off mechanism
  • LED lighting to indicate the heating status

Cons:

  • ​Narrow temperature range adjustment
  • ​Not highly accurate

4. Aquatop GH-50W – Fully Submersible Aquarium Heater

Aquatop Quartz Glass Submersible Aquarium Heater
  • Power: 50 Watts
  • Ideal tank size: Up to 13 gallons

Similar to the Aqueon Pro above, this Aquatop heater is fully submersible and includes suction cups to hold it in place in an upright vertical position inside the tank.

Inside, the heater has analog temperature settings and incorporates the use a knob to adjust to a higher or a lower temperature. However, it does not have a numbered rim around the knob to show the temperature figures.

Instead, the actual temperature readings are shown on the side of the heater tube using both Celsius and Fahrenheit scales. These run from 20ºC to 34ºC and 68ºF to 93ºF respectively.

Construction wise, the unit is made of a double glass layer, which makes it a bit delicate but provides very good insulation to the electrical components inside while also giving even heat distribution.

Pros:

  • ​Fully submersible with installation suction cups
  • Adjustable temperature settings
  • ​Wide 68ºF to 93ºF temperature range

Cons:

  • Recommended for installation in a vertical position only
  • Glass construction makes it very delicate

5. Eheim 3612090 – Aquarium Heater with Re-calibration Settings

Eheim Jager Thermostat Aquarium Heater
  • Power: 50 Watts
  • Ideal tank size: Up to 16 gallons

Instead of having a knob, this heater incorporates the use of a dial to select the desired temperature and has a readjustment ring that allows you to recalibrate the unit to + or - 8ºF for more accurate reading.

This recalibration ensures that the heater is set correctly so that the temperature set using the dial is the actual temperature that it achieves in the tank water. The result of this is a very accurate thermostat that does not cause under or overheating.

For safety, Eheim Jager’s unit features thermo safety control that shuts off the heater once it is pulled out of the water and turns it back on when reinserted into the water. This prevents dry running, which would otherwise ruin the heater’s coil.

Structurally, the product is made using lab-grade shatterproof glass that is quite strong and resistant to harmful chemical and biological substances as well as extreme temperature fluctuations. This makes it very durable.

Additionally, glass gives an even heat distribution by enlarging the heating surface when the unit is fully submerged in the water. 

Pros:

  • Recalibration feature for better accuracy
  • Thermo safety control to prevent dry running
  • Lab-grade shatterproof glass construction makes it very durable
  • Provides an even heat distribution

Cons:

  • ​Requires ​another thermometer when calibrating

6. ViaAqua VA 50Q – Aquarium Heater with a Ceramic Core

ViaAqua Quartz Glass Submersible Aquarium Heater
  • Power: 50 Watts
  • Ideal tank size: Up to 13 gallons

ViaAqua’s aquarium heater is characterized by a ceramic core, which is covered by a quartz glass casing. This improves on heat distribution but must be handled with care due to the delicate glass cover.

That said, you get highly visible temperature settings on the side, which are displayed in both degrees Celsius and Fahrenheit. These range from 20ºC to 34ºC and 68ºF to 93ºF on the respective scales.

Temperature adjustment is done via a knob on the upper part, which turns on either a plus or minus direction visibly on the scales. This makes it very easy to use.

Other features include a relatively low price tag, a small size (measuring 1.1 × 1.1 × 8.2 inches) and a lightweight design that weighs only 6.9 ounces.

Pros:

  • Ceramic core and glass casing distributes the heat evenly
  • Visible temperature setting
  • ​Celsius and Fahrenheit scales
  • ​Wide temp adjustment range

Cons:

  • ​Delicate glass casing

7. Penn Plax CH8100 – Affordable Aquarium Heater

Penn Plax Fully Submersible Aquarium Heater
  • Power: 100 Watts
  • Ideal tank size: Up to 20 gallons

Penn Plax is also a well-known brand in the aquarium accessories segment and made this affordable unit to be the best budget aquarium heater in this review. However, this does not mean that it lacks in terms of features.

For starters, the heater is fully submersible, with the option of placing it either horizontally or vertically inside the tank. It has a glass casing that covers the heating element on the bottom end to provide an even heat distribution.

The unit comes preset at a temperature of 76ºF, but this can be easily changed using an adjustment knob on the upper part.

Manual knob adjustments are usually a little bit less accurate and this is can be seen on its 1ºF accuracy rate. However, its dual scale (Celsius and Fahrenheit) makes it easy to adjust because the readings are clearly visible on the side of the heater tube.

Pros:

  • Affordable
  • Can be submerged in a horizontal or vertical orientation
  • Easy to use when adjusting temperature settings
  • Visible dual-scale gauge readings

Cons:

  • Glass casing is easy to crack
  • A bit less accurate

8. Lifegard Aquatics Aquarium Heater – Best Aquarium Heater for Large Tanks

Lifegard Aquatics Adjustable Aquarium Heater
  • Power: 300 Watts
  • Ideal tank size: 110 – 150 gallons

Lifegard Aquatics’ aquarium heater is a top-rated aquarium heater and this is primarily because of its high power size (300 watts), which makes it ideal for large 110 – 150-gallon aquariums.

This means that the unit is compatible most saltwater fish tanks because these are usually large in size so as to cushion the fish from various water quality fluctuations that might occur from time to time.

Functionally, the unit is submersible and has a temperature adjustment range of between 68 and 88ºF. Thermal protection keeps it in check just in case the temperatures exceed the set value, saving your fish from life-threatening temperatures.

To give you further trust in this product, the company made sure that the heater is UL certified, which means that it meets all the specific defined requirements of an aquarium heater.

Structurally, a huge chunk of the tube is covered with quartz glass, which is reinforced using a bi-metal construction, making it very strong and durable.

Pros:

  • Ideal for large 110 – 150-gallon tanks
  • Suitable for fresh and saltwater aquariums
  • Thermal protection safety feature
  • UL certified
  • Quartz glass with bi-metal construction makes it very durable

Cons:

  • High energy consumption
  • Narrow temperature adjustment range

9. Hydor T08203 – In-Line Aquarium Heater

Hydor In-Line External Aquarium Heater
  • Power: 300 Watts
  • Ideal tank size: 53 – 80 gallons

Unlike the products above, Hydor’s T08203 is an in-line aquarium heater that does not occupy space inside the tank. However, it must be connected to the return line of an external canister filter or sump.

It is important to note that the filter used must be functioning properly so as not to cause clogging inside the heater.

Temperature settings are adjustable on the heater using a dial, giving a range of 18 – 34ºC (65 – 93ºF). This range supports a wide variety of marine and tropical fish tanks, making it very versatile in terms of use.

The model is also available in 2 more variations, which are 200-watt, 26 – 53 gal 1/2-inch and 5/8-inch hose options. 

All of them are quite pricey but they have a high precision electronic temperature control feature that guarantees safety against the risk of overheating.

Pros:

  • ​Does not consume space in the tank.
  • ​3 size options
  • ​High precision electronic temperature control
  • Can be used on marine and freshwater tanks

Cons:

  • Expensive
  • Requires a properly functioning filter or sump so as not to clog

How to Buy the Best Aquarium Heater

How to Buy the Best Aquarium Heater

1. Type of Aquarium Heater

There are various types of aquarium heaters. These are:

Submersible heaters: Submersible heaters such as Aquatop's GH-50W are very efficient at heating because their entire bodies are placed inside the water. This means that all the heat produced goes directly into the water without any losses.

However, if they are too big, they might occupy the space that is meant for the fish. As such, the best submersible heater should be small in size.  

Immersible heaters: These are quite similar to submersible heaters except for the fact that not all the unit’s body is sunk in the water. The heater should be hung on the aquarium wall so that only the heating element can submerge into the water.

Such a setup means that the aquarium top cover needs to have an allowance for the upper part of the heater.

An important thing to note here is that immersible heaters are not ideal for saltwater aquariums because the salt might corrode the electrical circuitry if the water splashes inside.

However, the major disadvantage with these heaters is that they can electrocute the fish. If not properly secured, the heater may fall inside and short because the circuitry is not waterproofed.

In line heaters: With Hydor's T08203 as the ideal example, these ​external heaters ​must be connected to the return pipe of either a canister filter or a sump.

They are good options for larger tanks with larger fish because, with them, there is no contact between the heater and the fish. As such, the fish cannot break them as a result of high impact collisions.

However, they are harder to maintain because clogging may occur, especially if the filter is not functioning properly.

In sump heaters: These are usually much larger the in-line pumps but basically, work in the same way as them.

Substrate heaters: This type consists of a heating element buried under the gravel, from which the heat radiates to the rest of the tank. The problem with this type is that it is very difficult to set up.

Buying Advice: if you have a small fish tank, say up to 50 gallons in capacity, a submersible heater such as Cobalt Aquatics' 31004 is the best option. For bigger tanks, an in-line heater like Hydor's T08203 is your best bet.

2. Power

The power factor goes hand-in-hand with the tank size. For a 100-watt heater that is suitable for a 30-gallon tank (like Fluval's A772), this would be the same as buying two 50-watt heaters, each suitable for a 15-gallon tank.

Therefore, when buying any heater, it is important to compare the power and tank size in this manner before settling down on one.

3. Tank Size

Tank size is usually considered due to compatibility issues. You cannot buy a 50-gallon tank heater if you have a 20-gallon tank. Similarly, you cannot buy a 15-gallon tank heater if you have a 40-gallon tank.

However, for larger tanks, it is recommended to buy multiple small heaters as compared to a single large one because of two reasons.

One, multiple heaters will distribute heat more evenly around the tank as compared to one unit and two, in case one fails, the rest will at least maintain the water at a good temperature for the fish.

4. Adjustable Temperature

This aspect is usually considered in terms of the range of adjustable temperature. The bigger the range, the better the unit because it gives you more room to play with.

For instance, a 66-96ºF range like in Cobalt Aquatics' 31004 is much better than ​the 68-88ºF range in Aqueon's Pro​.

This is because it enables you to provide a much higher or a much lower temperature environment for the fish, depending on their preference.

5. Ease of Maintenance

At some point, you will have to clean the heater. Submersible and immersible units are usually very easy to clean, especially if they have glass insulations. All you have to do is wipe them clean. Check out ViaAqua's VA 50Q​.

In line and in sump heaters are a bit more complex to clean because you might be forced to disassemble the kit so as to wash it from the inside.

6. Additional Features

The most important additional feature that an aquarium heater should have is a thermal protection feature. This shuts down the unit automatically when the thermostat fails ​so as to prevent continuous heating to the point of boiling the fish alive.

​For this, most highly advanced heaters such as Lifegard Aquatics' Aquarium Heater contain this feature. 

How to Install the Aquarium Heater

How to Install the Aquarium Heater

Since submersible aquarium heaters are the most common options, we will use them as an example. They are installed using the following steps:

1. Inspect the heater before installation to ensure that it has no damages or defects

2. Identify the best location to fit the heater in your aquarium. This should be close to the return pipe from the filter in order to utilize that current to spread the heat.

3. Clean the glass surface on the identified area and attach the suction cups that come with the heater.

4. Adjust the heater temperature then install it inside the tank using the attached suction cups.

5. Let it rest for about 5 minutes so that the casing can adjust to the water temperature. This is important because sudden temperature spikes might cause cracks, especially in glass.

6. Place an external thermometer on the opposite side of the heater, if the heater does not have a built-in thermometer.

7. Turn on the heater and let it operate for about a day without the fish inside the tank. During this time, keep monitoring the thermometer in order to check whether the water temperature is maintained at the set temperature. Reset and recalibrate if needed.

8. If all is well, add the fish to the tank and continue monitoring throughout.

FAQs

1. Is the aquarium heater really necessary?

This depends on the type of fish that you want to keep. If you intend to keep tropical fish and you live in an area where the room temperature is very cold, it is necessary to have an aquarium heater.

However, if you want to keep temperate fish, these can survive well in temperatures that range from 18 - 22ºC, meaning that they can survive in room temperature. In such a case, aquarium heaters are not necessary.

2. Where should I place the aquarium heater?

For a submersible aquarium heater, the best area to place it is across or near the water flow channels. This is close to the inlet or outlet to the filter.

At this position, the flowing water will greatly help distribute the heat throughout the entire tank.

3. How much electricity does the aquarium heater use?

This generally depends on two things: the size of your tank and the temperature adjustment.

As a reference point, a heater heating a 30-gallon tank to 72ºF consumes about 110 kWh. The same tank heated to 82ºF requires 440 kWh.

There is no exact calculation to answer this question but the estimates above might help you determine how much electricity an aquarium heater consumes.

4. Is the aquarium heater easy to clean? And how often to clean?

This depends on the type. Submersible and immersible are usually very easy to clean because you only need to wipe them.

In line and in sump heaters are harder to clean since the heated water channels are hidden inside the unit, meaning that some disassembly might be necessary to access these parts.

Cleaning should be done as you clean or change the tank water so that everything that goes back inside is fresh.

5. Can I put a heater in a plastic fish tank?

Yes, you can. Aquarium heaters are not meant to boil the water and thus, the little warming effect that they have on the water will not affect acrylic tanks. 

6. How many watts does my aquarium need?

This mostly depends on the temperature increase that you want as well as the size of your tank. A guide to help you with this is shown below.

5 gal

10 gal

20 gal

30 gal

55 gal

75 gal

90 gal

5ºF increase

50 W

50 W

50 W

100 W

150 W

200 W

200 W

10ºF increase

50 W

50 W

100 W

100 W

150 W

200 W

250 W

15ºF increase

50 W

100 W

100 W

150 W

200 W

250 W

250 W

Conclusion

They might look small but by going through this aquarium heater review, it is clear that there is a lot of information about these gadgets that must be understood before making any purchase.  

​That said, we highly recommend Fluval's A772 as the overall best aquarium heater because it hosts a lot of high tech features such as a color-coded temperature display and dual sensors for high accuracy. 

Cobalt Aquatics' 31004 is also an excellent choice but if you are on a tight budget, buy Penn Plax's CH8100.

Sources


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