Tanks & Accessories

10 Best Aquarium Thermometers of 2020

Best Aquarium Thermometer

Photo: Risepro

If you are an aquarist and you live in a cold area, chances are that you have a heating mechanism to warm up your aquarium so as to create a conducive environment for your fish.

With this, it is important to keep track of temperature changes in the water in order to stabilize it if it fluctuates or to make any adjustments. This is because such fluctuations cause stress to the fish.

Even if your heater has a built-in thermometer, an external one will help you double-check the readings just in case the built-in unit fails.

That said, this article gives you an in-depth review of the best aquarium thermometers so as to make it easier for you to get a good one for your tank.

10 Best Aquarium Thermometers – Review

IMAGE

​PRODUCT

​FEATURES

Zacro FBA_ZDT1-AUX-1

1. Zacro FBA_ZDT1-AUX-1 (Best Overall)

  • Highly accurate digital thermometer (to within 0.1°)
  • Submersible probe with a 24.88-inch-long cable
  • Fahrenheit and Celsius display units
  • -50 to 70°C temperature range
American Thermal BC002008

2. American Thermal BC002008 (Best Stick-on Design)

  • Analog scale stick-on thermometer
  • 19 to 29°C temperature range
  • Lightweight (0.32 pounds)
Sukragraha Traditional Stick on Aquarium Thermometer

3. Sukragraha Traditional Stick on Aquarium Thermometer (Stick-on Design with Colored Readings)

  • Colored temperature readings
  • 18 to 34°C temperature range
  • Fahrenheit and Celsius scales
  • Self-adhesive back
Marina 11201A1

4. Marina 11201A1 (Best for the Money)

  • Affordable
  • 0 – 50°C temperature range
  • Safety zone indicator
  • Fahrenheit and Celsius scales
Keynice AP-185-USB

5. Keynice AP-185-USB (Rechargeable Battery)

  • Digital thermometer with a rechargeable battery
  • -50 to 110°C range
  • NTC probe with a meter long cable
  • +/- 1°C accuracy
Risepro TM-4

6. Risepro TM-4 (Easy to Install Digital Design)

  • Includes 2 suction cups for easy mounting
  • -50 to 70°C temperature range
  • +/- 1°C accuracy
  • 1 meter (39-inch) probe cable
LCR Hallcrest A-1005

7. LCR Hallcrest A-1005 (Easy to Read stick-on Design)

  • Liquid crystal temperature indicator
  • 66 – 84°F temperature range
  • Color-coded display
HDE Digital Aquarium Thermometer

8. HDE Digital Aquarium Thermometer (Best Set)

  • 3-piece set
  • Ideal for fresh and saltwater tanks
  • Includes batteries and a large LCD screen
  • +/-0.1° accuracy
General Tools AQ150

9. General Tools AQ150 (High-Low Alarm)

  • High-and-low temperature alarm
  • Ambient and remote temperature sensors
  • -50 to 70°C with +/-0.5°C accuracy
  • Fahrenheit and Celsius display options
JW Pet 21600

10. JW Pet 21600 (In-Tank Thermometer with Magnetic Installation)

  • Magnetic installation
  • -1 to 40°C temperature range
  • Safe zone marking

PRODUCT

1. Zacro FBA_ZDT1-AUX-1

(Best Overall)

Zacro FBA_ZDT1-AUX-1
  • Highly accurate digital thermometer (to within 0.1°)
  • Submersible probe with a 24.88-inch-long cable
  • Fahrenheit and Celsius display units
  • -50 to 70°C temperature range

2. American Thermal BC002008

(Best Stick-on Design)

American Thermal BC002008
  • Analog scale stick-on thermometer
  • 19 to 29°C temperature range
  • Lightweight (0.32 pounds)

3. Sukragraha Traditional Stick on Aquarium Thermometer

(Stick-on Design with Colored Readings)

Sukragraha Traditional Stick on Aquarium Thermometer
  • Colored temperature readings
  • 18 to 34°C temperature range
  • Fahrenheit and Celsius scales
  • Self-adhesive back

4. Marina 11201A1

(Best for the Money)

Marina 11201A1
  • Affordable
  • 0 – 50°C temperature range
  • Safety zone indicator
  • Fahrenheit and Celsius scales

5. Keynice AP-185-USB 

(Rechargeable Battery)

Keynice AP-185-USB
  • Digital thermometer with a rechargeable battery
  • -50 to 110°C range
  • NTC probe with a meter long cable
  • +/- 1°C accuracy

6. Risepro TM-4

(Easy to Install Digital Design)

Risepro TM-4
  • Includes 2 suction cups for easy mounting
  • -50 to 70°C temperature range
  • +/- 1°C accuracy
  • 1 meter (39-inch) probe cable

7. LCR Hallcrest A-1005

(Easy to Read stick-on Design)

LCR Hallcrest A-1005
  • Liquid crystal temperature indicator
  • 66 – 84°F temperature range
  • Color-coded display

8. HDE Digital Aquarium Thermometer

(Best Set)

HDE Digital Aquarium Thermometer
  • 3-piece set
  • Ideal for fresh and saltwater tanks
  • Includes batteries and a large LCD screen
  • +/-0.1° accuracy

9. General Tools AQ150

(High-Low Alarm)

General Tools AQ150
  • High-and-low temperature alarm
  • Ambient and remote temperature sensors
  • -50 to 70°C with +/-0.5°C accuracy
  • Fahrenheit and Celsius display options

10. JW Pet 21600

(In-Tank Thermometer with Magnetic Installation)

JW Pet 21600
  • Magnetic installation
  • -1 to 40°C temperature range
  • Safe zone marking

1. Zacro FBA_ZDT1-AUX-1Our Pick for the Best Aquarium Thermometer

Zacro LCD Digital Aquarium Thermometer

Photo: Zacro

  • Temperature Range: -50°C to 70°C
  • Dimensions: 2.2 × 1.5 inches
  • Weight: 0.32 ounce
  • Battery: LR44 button cell

Zacro’s aquarium thermometer takes the overall top spot because it is highly accurate, giving its temperature readings to within 0.1°. This makes it ideal for extremely sensitive aquarium livestock that prefer to stick to a very narrow temperature range.

To sense the temperature, a submersible probe is connected to the thermometer via a 24.88-inch-long cable, and this makes it possible to submerge it into the fish tank while the main unit remains outside the water. This is very important because the thermometer is not waterproof.

Once the measurements are sensed, the results are displayed live on a large and easy to read LCD screen in either Fahrenheit or Celsius units. A slider switch is used to change between these two, enabling you to get temperature readings in your most preferable way.

The benefit of using having a digital thermometer with such a display is that the temperature values are very easy to read as compared to scale readings on other types of thermometers.

However, the unit does require a power source and this is supplied using one LR44 button cell, which is included in the package.

Pros:

  • Very accurate readings to within 0.1°.
  • Long 24.88-inch cable makes it possible to submerge the probe while the thermometer is above water
  • Large and easy to read LCD screen
  • Gives readings in degrees Celsius and Fahrenheit
  • Comes with its battery

Cons:

  • Not waterproof

2. American Thermal BC002008Best Stick-on Aquarium Thermometers

American Thermal Aquarium Horizontal Thermometer

Photo: American Thermal

  • Temperature Range: 19°C to 29°C
  • Dimensions: 7.4 × 1 inches
  • Weight: 0.32 ounce

American Thermal’s stick-on unit is a top-rated aquarium thermometer that is very lightweight and requires to be mounted on the outside of an aquarium.

The thermometer’s movable characteristic gives it a very big advantage because it can be unglued from the external aquarium wall, stuck on to a different place and still work.

For installation, this piece must be placed in a horizontal orientation because its measurement readings are printed on the material in such a way that they can be comfortably read in this position.

On the downside, the readings that the thermometer can handle are in a narrower range of 19°C to 29°C and this limits the extent to which you can use it. Additionally, the unit is not as accurate as a digital one.

However, unlike digital thermometers, batteries are not required for this to operate. This means you don’t have to worry about not getting your reading once the batteries run out of charge.

Pros:

  • Movable stick on thermometer
  • Horizontal placement makes it easier to read and us.
  • Lightweight

Cons:

  • ​Narrow temperature range
  • Not as accurate as a digital thermometer

3. Sukragraha Aquarium ThermometerStick-on Thermometer with Colored Readings

Sukragraha Traditional Stick on Aquarium Thermometer

Photo: Sukragraha

  • Temperature Range: 18°C to 34°C
  • Dimensions: 5.12 × 0.71 inches
  • Weight: 0.32 ounce

Sukragraha’s stick-on aquarium thermometer is quite unique because displays different temperatures using different colors, using blue for the actual water temperature and brown for the higher temperatures. This makes its use very intuitive and much easier to read.

Although the strip’s readings are in a smaller range (18-34°C), they are indicated in both °C and °F, enabling you to use the scale that you prefer most. Additionally, they are very easy to read because the values are only given in discrete numbers.

On installation, the product is self-adhesive, with a sticky back that easily sets on the tank wall. If you install it incorrectly, no need to worry. The strip is movable, which means you can remove it from the surface and stick it back correctly or onto a different surface.

Additionally, the set contains 10 pieces and therefore, if one piece gets torn apart as you try to move it, you have 9 more at your disposal.

The only disadvantage with this product is that it might be a bit difficult to read the temperature value in low light.

Pros:

  • Gives temperature readings in both °C and °F
  • Displays different temperatures using different colors
  • Self-adhesive
  • Movable
  • Comes as a set of 10 thermometers

Cons:

  • Difficult to read in low light
  • Smaller temperature range

4. Marina 11201A1Best Aquarium Thermometer for the Money

Marina Floating Aquarium Thermometer with Suction Cup

Photo: Marina

  • Temperature Range: 0°C to 50°C
  • Dimensions: 4.25 × 1 inch
  • Weight: 0.8 ounce

Marina’s floating aquarium thermometer is the most affordable product in this review but this does not mean that it is substandard.

For starters, the unit is very easy to read. It has a scale that gives the temperature readings in both °C and °F in the range of 0 – 50 and 32 – 122 respectively on its clearly labeled glass wall.

Additionally, it has a safety zone indicator that marks the favorable temperature range for most tropical fish so that you can know whether your tank’s water is conducive at a glance. This makes it one of the best floating aquarium thermometers.

However, it is very small in size (4.25 inches tall) and this means that its readings are very compressed and thus, reading between the lines might be a bit difficult.

The good thing though is that it gives accurate readings because it is placed inside the water and thus, gets the actual temperature from the inside.

For installation, this unit comes with a suction cup, which holds it firmly in position. The only disadvantage is that this suction cup might leave marks on your tank wall after some time.

Pros:

  • Affordable
  • Gives temperature readings in both °C and °F
  • Safety zone indicator
  • Gives accurate readings because it is placed inside the water
  • Comes with a suction cup for installation

Cons:

  • Compressed temperature scale makes it difficult to determine the actual temperature

5. Keynice AP-185-USBDigital Thermometer with a Rechargeable Battery

Keynice Digital Thermometer

Photo: Keynice

  • Temperature Range: -50°C to 110°C
  • Dimensions: 1.89 × 1 inch
  • Weight: 1.6 ounces
  • Battery: Rechargeable battery

Keynice’s product is one of the best digital aquarium thermometers simply because it features a rechargeable battery and has a very wide temperature range of -50 to 110°C.

Due to this large range, this product has a very wide application area, which includes measuring the temperature in flower houses, HVAC air ducts, server rooms, engine rooms and of course, aquariums.

An NTC probe is featured for sensing the temperature levels in the water, and it is connected to the thermometer via a 1-meter long cable. This means that it can be submerged deep into the water for more accurate readings, which in this unit is +/- 1°C.

The readings are shown on its large LCD backlit color display and can be given in either °C or °F. A short-circuiting pull switch at its back is used to change between these two, which might be a bother to some, pulling and pushing it back is quite a simple process.

For charging, USB is used, which means you can hook it up to your computer, power bank or USB charger while it is still being used.

Pros:

  • Rechargeable battery
  • Wide temperature range of -50 to 110°C
  • Remote NTC probe on a 1-meter long cable for temperature sensing
  • Large LCD backlit color display
  • Convenient USB charging system

Cons:

  • Short-circuiting pull switch might be a bother to use when switching from °C to °F
  • Not as accurate as other digital thermometers such as Zacro’s unit above

6. Risepro TM-4Easy to Install Digital Aquarium Thermometer

Risepro Digital Aquarium Thermometer

Photo: Risepro

  • Temperature Range: -50°C to 70°C
  • Dimensions: 2.3 × 1.5 inches
  • Weight: 0.3 ounce
  • Battery: LR44 button cell

Risepro’s aquarium thermometer is also very affordable and can be easily installed because it comes with two suction cups for mounting onto the outside tank wall. Once installed, the included meter-long cable for dips the probe into the water to get the temperature readings.

You also get a relatively wide -50 to 70°C or -58 to 158°F temperature range, a sliding button for easy switching between these two units, a large LCD screen, and two LR44 button cell batteries.

On the downside, the thermometer’s accuracy is a bit off at +/-1°C, but this is much better than in non-digital units.

An important thing to note is that the digital thermometer itself is not waterproof and thus, it should only be mounted outside the aquarium.

Pros:

  • Comes with two suction cups for a quick set up
  • Affordable
  • Displays temperature reading both in °C and °F
  • Meter long cable suspends the probe deep into the water
  • Comes with its button cell plus a spare one

Cons:

  • Not waterproof
  • Accuracy is not that high as compared to other digital units

7. LCR Hallcrest A-1005Easy to Read stick-on Aquarium Thermometer

LCR Hallcrest A-1005 Aquarium Thermometer

Photo: LCR Hallcrest

  • Temperature Range: 19°C to 29°C
  • Dimensions: 7.3 × 0.75 inches
  • Weight: 0.6 ounce

With its liquid crystal temperature indicator, this A-1005 is quite easy to read, and it has a sticky back that mounts vertically outside your fish tank for easy installation.

This also makes the unit easily removable in instances where you may want to clean the tank or use it on a different aquarium.

On the scale, this piece only features measurements given in °F on a range of 66 – 84, which is roughly 19 – 29°C.

Though this is a small range, the liquid crystal temperature indicator makes it quite accurate and, as explained above, easy to read. However, in low lighting, an external lighting source is required in order to make the reading more visible.

A color code is used to display the temperatures, with the green box showing the actual temperature, brown box showing the higher reading and blue box showing the temperature below. With these, you can figure out and also monitor the temperature changes easily.

Pros:

  • Easy-to-read liquid crystal temperature indicator
  • Easy to install by sticking onto the wall surface
  • Movable
  • Liquid crystals with a color-coded display

Cons:

  • A bit difficult to read in the dark

8. HDE Digital Aquarium ThermometerBest Aquarium Thermometer Set

HDE Digital Aquarium Thermometer

Photo: HDE

  • Temperature Range: -50°C to 70°C
  • Dimensions: 2 × 1.25 inches
  • Weight: 3.84 ounces
  • Battery: LR44 button cell

HDE’s digital aquarium thermometer is certainly not very affordable as compared to the other units but it comes as a set of 3 digital thermometers, which make the cost per unit very low. This makes it the best thermometer set for people with multiple tanks.

Additionally, the units are great for fresh or saltwater aquariums and thus, can be used on all kinds of tanks from amphibian or reptile terrariums to regular fish tanks and many others. Therefore, if you have multiple tanks, these 3 pieces are compatible with all of them.

In terms of design, this thermometer has a large and easy to read LCD screen that can display the temperature readings in either Fahrenheit or Celsius, depending on the setting that you make using the slider switch below the screen.  

However, it is important to note that this unit is not waterproof and thus, it should not be submerged into the water. Only the probe should go into the water.

Other features include the inclusion of LR44 batteries and +/-0.1° accuracy, making it one of the best digital aquarium thermometers.

Pros:

  • Comes as a pack of 3 thermometers
  • Compatible with fresh and saltwater tanks
  • Large and easy to read LCD screen.
  • Comes with its batteries
  • Very high accuracy

Cons:

  • Not waterproof.

9. General Tools AQ150Aquarium Thermometer with High-Low Alarm

General Tools AQ150 Aquarium Thermometer

Photo: General Tools

  • Temperature Range: -50°C to 70°C
  • Dimensions: 2.9 × 2 inches
  • Weight: 1.6 ounces
  • Battery: CR2032 button battery

General Tools’ aquarium thermometer is characterized by a high-low-temperature alarm, which ensures that you keep the water temperature within the set range. This alarm automatically turns on when the water temperature goes below or above the limits of this range.

The thermometer can also be used to measure the room or water temperature by toggling with the ambient and remote sensor temperature buttons, making its use very versatile.

Setting to ambient measures the room temperature while the remote sensor setting requires a remotely connected probe so as to get the readings from it. 

Other features include a large LCD display, a range of -50 to 70°C, toggling between Fahrenheit and Celsius display and an accuracy of +/-0.5°C. However, this piece is quite expensive. 

Pros:

  • High and low-temperature alarm
  • Ambient and remote temperature sensing
  • Large LCD display
  • Can display the temperature in either Fahrenheit or Celsius
  • A wide range of -50 to 70°C

Cons:

  • Expensive

10. JW Pet 21600In-Tank Thermometer with Magnetic Installation

JW Pet Company Smarttemp Aquarium Thermometer

Photo: JW Pet

  • Temperature Range: -1°C to 40°C
  • Dimensions: 5.6 × 0.5 inches
  • Weight: 1.12 ounces

JW Pet’s Smarttemp unit is an in-tank aquarium thermometer that is secured in place using a magnet and thus, no suction cups are required.

This makes it superbly easy to install because all you have to do is make sure that the magnet on the outside is holding the thermometer firmly on the inside.

In terms of size, the Smarttemp measures 5.6 inches in height and on this column, it can measure a range of -1 to 40°C or 30 to 104°F.

A safe zone is clearly marked in green on the scale’s midpoint and it shows the safe temperatures that are conducive for keeping tropical fish, making the work easier for you.

For accuracy, this unit is correct to within +/-1.5°F, which is a good option relative to other in-tank thermometers, but still not as good as in digital thermometers. 

Pros:

  • Magnetic installation
  • Relatively wide range for an in-tank thermometer.
  • Safe zone marking

Cons:

  • Not very accurate

How to Buy the Best Aquarium Thermometer

How to Buy the Best Aquarium Thermometer

1. Type of Aquarium Thermometer

Digital

Digital aquarium thermometers are the most advanced of the 3 types of aquarium thermometers and consequently, are more expensive.

However, they have features such as LCD screens for easy reading, remote sensor probes, high accuracy and have alert features that sound an alarm when the water temperature is too low or too high past the set range.

Pros:

  • Remote temperature sensing using a probe
  • Easy to read
  • Highly accurate
  • Features alert functionalities

Cons:

  • Expensive
  • Requires batteries to run

Standing or floating

This type is usually placed in the water and this gives it the benefit of getting the direct temperature reading from the inside.

A variety of them exist, for instance, those that are stuck inside the tank using suction cups, others are suspended using magnets while the rest simply float on the water.

Instead of alarm systems, these units usually have safe zones indicated on them using a green color, and these can be used to check if the temperature is suitable for tropical fish or not.

On the downside, most of them are made of glass, which is very brittle, and they are not as accurate as digital units.

Pros:

  • Features safe zones
  • Can be placed almost anywhere inside the tank
  • They are not affected by room temperature since they are submerged
  • Less expensive than digital thermometers

Cons:

  • Brittle glass construction
  • No alert features
  • Less accurate than digital thermometers

Stick on

This is the most widely used type because it is affordable and most tanks come with it as an accessory.

Although some refer to these as LCD thermometers, this is not entirely true. Some of them have colors that indicate the current water temperature and this is what makes people think that they have LCD. However, these colors are usually very dull and thus, hard to read in low light.

The other disadvantage with these is that they can be affected by room temperature. Therefore, for the best results, avoid placing them under direct sunlight or below the gravel so as not to affect its accuracy.

On the bright side, most stick-on units are easy to install, movable and feature Fahrenheit and Celsius scales for more customized readings.

Pros:

  • Affordable
  • Easy to install
  • Movable

Cons:

  • Hard to read in low light
  • Not as accurate as digital thermometers

#2. Temperature Range and Accuracy

A thermometer’s temperature range is important to consider because it gives the limits to which the unit can be used.

For aquariums, since freezing and boiling is not required, a range of about 10°C to 40°C is enough for the job. The goal here is to monitor the water and ensure that it remains at the conducive level, which falls within this bracket.

In addition to that, the best thermometer should be accurate to within less than +/-1°C so that it does not throw you off while thinking that you have the correct reading.

In this case, thermometers such as Zacro's FBA_ZDT1-AUX-1 are best. 

3. Readability

Of course, a thermometer is only as good as its readability. If you cannot be able to read the scale, it will be useless to you.

Digital thermometers such as General Tools' AQ150 are the easiest to read because they display the value clearly on a big screen.

Color changing stick-on units such as Sukragraha's piece are also easy to read since they highlight the actual temperature value in a different color.

However, mercury-based ones can be challenging because getting the exact point that the red line has settled on can be a big task, especially if your eyes are weak.

4. Ease of installation and usage

Floating and stick-on thermometers are usually very easy to install using either suction cups, magnets or sticky surfaces for the stick-on type. They are also easy to use because they are waterproof and thus, no special care is required.

However, digital thermometers require to be installed carefully because they can be damaged by water and they require some few extra steps when using them but this is usually not very complex.

How to Read an Aquarium Thermometer Sticker/ Strip

While installing a thermometer strip is easy, reading it might be a challenge. However, the following colors will help you figure out how it’s done.

Blue: Blue usually indicates the temperature below the tank’s actual temperature

Red: Red indicates the exact value above the actual value.

The real value: The real water temperature will be in the middle of these two and in a green color. This is what you should read as the actual water temperature.

Conclusion

As you can see, there are different kinds of aquarium thermometers. Choosing one for your tank, especially as a beginner, might be a hard task but we recommend Zacro's FBA_ZDT1-AUX-1.

All in all, after reading through, it should be easier to pick the best aquarium thermometer that suits your tank’s needs.

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