Best Aquarium Thermometers in 2021 [Reviews & Guide]


The water temperature in the aquarium is critical to monitor to keep your fish fresh and healthy. Some fish need warmer water, and some fish need cold water, so there are various types of fish to be protected in your fish water aquarium.

It would help if you chose the most straightforward thermometer, which can give you the convenience to adjust the thermometer and monitor the temperature inside the aquarium.

Best Quality
HDE 2 Pack LCD Digital Fish Tank Aquarium Thermometer...
Best Overall
Marina Floating Thermometer for Betta Fish Tank with Suction...
Best Value
BodyMed Digital Moist Heating Pad with Auto Shut Off,...
HDE 2 Pack LCD Digital Fish Tank Aquarium Thermometer...
Marina Floating Thermometer for Betta Fish Tank with Suction...
BodyMed Digital Moist Heating Pad with Auto Shut Off,...
  • HDE Digital
  • Marina Floating
  • Zacro Digital
Best Quality
HDE 2 Pack LCD Digital Fish Tank Aquarium Thermometer...
HDE 2 Pack LCD Digital Fish Tank Aquarium Thermometer...
  • HDE Digital
Best Overall
Marina Floating Thermometer for Betta Fish Tank with Suction...
Marina Floating Thermometer for Betta Fish Tank with Suction...
  • Marina Floating
Best Value
BodyMed Digital Moist Heating Pad with Auto Shut Off,...
BodyMed Digital Moist Heating Pad with Auto Shut Off,...
  • Zacro Digital

A well-designed thermometer must be capable of submerging in the water, or it must have a probe to attach to the cable, it is used for getting an accurate water temperature.

The mercury and color-changing crystal thermometers also work efficiently, so the digital thermometer is not needed. 

Most of the fishes can live only in specific water temperatures, so monitoring the readings is very important to the health and happiness of your fish.

Some thermometers come with an alert feature, which can help you to set off an alarm whenever the water temperature changes from the average temperature.

You must have a clear idea before picking the thermometer. It will be designed with lead and mercury substances, which can harm your fish when it breaks, so choose the best aquarium thermometer to keep your fish alive for a long time.

After 48 hours of research, we’ve made the list of the best aquarium thermometer for your fish. It was helpful for your purchase.

Best Aquarium Thermometers – 10 Picks Reviewed

1. Marina Floating Thermometer with Suction Cup

The Marina Floating Thermometer with Suction Cup is accurate, and it is easy to read, you can float in the water and get an accurate reading.

Arctic Silver 5 Thermal Paste

Marina Floating Thermometer with Suction Cup

  • Brand: Marina
  • Type: Floating thermometer
  • Height: 4.25 inches
  • Weight: 0.8 ounces
  • Color: Basic pack

It is effortless and easy to use a thermometer, you can float it in a vertical position, and it comes with a suction cup so you may easily attach it to the walls of the aquarium.

It can be able to measure 4.25 inches tall by floating it on the wall inside the tank along with the suction cup.

The temperature readings can be either in Celsius or Fahrenheit with a click of a single button you can easily switch between Fahrenheit and Celsius, and also has a safe zone indicator so you can quickly identify whether it goes outside the safe temperature.

It is effortless to use this aquarium thermometer because it does not require any batteries but gives an exact temperature reading 100 percent of the time.

It has the potential to protect the fish from unsafe heat so that it can stay for a long time without any damages.marina floating

An user shared his experience of using Marina Floating thermometer for his aquarium.

The Marina Floating thermometer does not use the LCD display to measure, but it makes use of the time-tested method of using mercury to measure the accurate readings.

The overall design of this thermometer can be sleek and compact; it is well designed with a lightweight material, so you can easily carry it.

This thermometer comes with a suction cup, so it is easy for you to stick it inside your aquarium wall. It is the best budget aquarium thermometer so it perfectly suits you.


  • Reasonable price
  • Doesn’t require batteries
  • Has safe zone indicator


  • No major issues to concern

2. HDE Digital Aquarium Thermometer

It is straightforward to track the water temperature with this HDE Digital Aquarium thermometer; it is enormous and has an easy-to-read LCD display screen.

Arctic Silver 5 Thermal Paste

HDE Digital Aquarium Thermometer

  • Brand: HDE
  • Type: Digital thermometer
  • Height: 2*1.25 inches
  • Weight: 0.64 ounces
  • Color: Black

It gives a more versatile temperature range between -50 and +70 degrees Celsius. This HDE Thermometer will be very convenient for you to monitor the temperature of water in the fish tank.

It can be stuck easily on the walls of the aquarium glass to offer an accurate reading both in Fahrenheit and Celsius.

The suction cups are fixed at the outside of the tank, and the temperature gauge is kept inside the tank for attaining the perfect reading.

It is constructed with two main components one is a sensor, and the other is a display. The end portion is designed with a suction cup that is attached to give a secure fit to the aquarium.

It is one of the most accurate digital aquarium thermometers on the market.

If you submerge the sensor inside the water, then it is possible to get an exact temperature.

This thermometer has a built-in LR44 battery so you can be ready to measure the reading, if you need to switch on the thermometer then press the “on” button, now you can be able to measure the aquarium’s temperature and check the fish health.

It is also possible to switch easily between Celsius and Fahrenheit.


  • Clear digital screen
  • Simple and large thermometer
  • Gives measurements in both Celsius & Fahrenheit


  • Doesn’t have temperature alarm

3. Zacro Digital Aquarium Thermometer

The Zacro Digital Aquarium thermometer is designed with an LCD display, so it will be easy to read; it also shows the temperature either in Fahrenheit or Celsius.

Arctic Silver 5 Thermal Paste

Zacro LCD Digital Aquarium Thermometer

  • Brand: Zacro
  • Type: Digital thermometer
  • Height: 2.17 x 1.46 inches
  • Weight: 0.32 ounces
  • Color: Black

It is powered up with an LR44 button battery cell, so it is highly durable and can last for a long time; another battery can easily replace it.

This thermometer can have an extraordinary temperature range; the regular reading can be -50 degrees Celsius to +70 degrees Celsius. It is one of the most versatile thermometers.

It adds more convenience to you by having the suction cup so you can easily stick the thermometer just at the exterior part of your fish tank.

It has a compact design; the sensor should be submerged into the water to gauge the exact temperature.

When you plan to buy a fish tank, it is essential to see whether the fish are staying comfortable and have the correct temperature.

If you would like to purchase the best aquarium thermometer with a probe, then you can choose this one.

The Zacro LCD digital Aquarium thermometer is the best for monitoring the accurate reading. It produces an independent text at both salt and freshwater tanks.

It is possible to float the thermometer into the fish tank in a vertical position so that you may quickly get the aquarium’s temperature correctly.

It is not necessary to submerge the aquarium thermometer into the tank, place the probe inside it. This equipment is not too heavy; it is designed smoothly and conservatively.


  • Simple to operate
  • Elegant and compact design
  • Easy to mount the display


  • Small power supply wire

4. American Thermal Instruments Aquarium Thermometer

It is one of the best aquarium thermometers which offer an accurate reading; it is very compact and easy to carry aquarium thermometer, which uses many varieties of touching colors.

Arctic Silver 5 Thermal Paste

Main Features

  • Brand: American Thermal
  • Type: Floating thermometer
  • Height: 5 x 6.75 inches
  • Weight: 0.8 ounces
  • Color: Blue

It gives a lot of conveniences to read the temperature because it is properly designed, this is very easy to install peel off the film on the backside of it and gently stick it to the inside of your aquarium.

The thermometer should be completely submerged for getting an efficient reading. It doesn’t use an LCD display; it merely uses the color-changing crystals to indicate the temperature range.

The color of the crystals varies depending upon the temperature inside the tank. It is mandatory to compare the color with a color chart to attain accurate reading.

It would help if you chose the place to fix the thermometer, whether to fix below the waterline or outside of the aquarium.

It weighs about 0.3 ounces, and it is possible to fix the thermometer horizontally, the back portion of the thermometer helps to sense the temperature inside the aquarium through the glass, the reading is shown in a digital display of the temperature.

It is the best idea to use adhesive to peel off the film. The liquid crystals can be used to remove it and then place in a proper location gently.


  • Clear display
  • Sticks perfectly
  • Comes with color changing crystals


  • Have to use flashlight to read 

5. Lifegard Aquatics Digital Temp Alert

The Lifegard Aquatics thermometer has a large display thermometer for both freshwater and marine aquariums; it also can measure room temperature as well as the water temperature inside the aquarium.

Arctic Silver 5 Thermal Paste

Lifegard Aquatics Digital Temp Alert

  • Brand: Lifegard
  • Type: Digital thermometer
  • Height: 6 x 8.2 inches
  • Weight: 6.4 ounces
  • Color: Black

It has a probe that measures the aquarium temperature, and the internal thermometer measures the room temperature.

The Digital Temp Alert is designed with a programmable alarm, which alerts you when the temperature is above or below the expected range. 

It is the best aquarium thermometer with an alarm. It does not use the LCD thermometer to measure the readings; it just uses the regular measuring tool to take the air temperature. This thermometer can be used in saltwater and freshwater aquariums.

The suction cup is designed to stick it on the side of any aquarium; it has easy to read digital display so you can note the temperature without any mistakes.

It comes with a simple user interface, so it will be very convenient to use even for beginners. The suction cup is attached to the in-tank probe so you can fix it to the aquarium glass quickly, there are four levels of temperatures if a red light indicates then the temperature is out of range.


  • Different types of temperature alert
  • Measures both room and tank temperature
  • Able to use both fresh and saltwater


  • A bit pricey

6. TOOGOO Digital LCD Fish Aquarium Thermometer

The TOOGOO Digital Aquarium Thermometer is very easy to use and offers a wide temperature range; it has a compact design and does not require much space.

Arctic Silver 5 Thermal Paste

TOOGOO Digital LCD Vivarium Thermometer

  • Brand: Toogoo
  • Type: Digital thermometer
  • Height: 25 x 12 inches
  • Weight: 3.52 ounces
  • Color: Black

It comes with a high-quality LCD display, which helps you to mark the temperature accurately; it is not too heavy just 3.5 ounces, so you may not feel adamant about installing it using the suction base.

It is powered up with a DC 1.5V LR44 button battery so it can last for a long time.

You can get accurate readings using this thermometer either in Fahrenheit or Celsius; it is highly durable, so it will not break when you drop it accidentally.

To save the battery life, just power off the thermometer display and turn on when it is needed to see the temperature.

The portable digital LCD thermometer can measure the temperature range from -10 degrees Celsius to +70 degrees Celsius.

This device is mounted with a high-quality suction base to ensure that the thermometer does not fall inside the fish tank and end up breaking.

There is a sensor attached to the aquarium thermometer, so it is not needed to fix the device directly back to the fish tank.

You can charge it with a powerful battery, which also works when plugged.


  • Accurate reading
  • Good battery life
  • Durable and unbreakable


  • No mounting suction cup

7. Pet Magasin Digital Thermometer

It is a unique digital thermometer but very useful, and it also acts as a hygrometer because it is capable of reading the humidity in the air.

Arctic Silver 5 Thermal Paste

Pet Magasin Digital Thermometer

  • Brand: Pet Magasin
  • Type: Digital thermometer
  • Height: 3 x 0.5 inches
  • Weight: 1.3 ounces
  • Color: Green and Green

It is a very compact and affordable digital thermometer that allows you to monitor the exact temperature. It is designed with an elegant and convenient LCD display that is large and easy to read the temperatures.

It will show the water temperature with a lot of digital accuracies and has a large LCD display screen to read.

It is suitable for both aquariums and terrariums, which can be easily readable using the big screen. You can stick the Pet Magasin on the outside of your aquarium glass, which will make use of some specific digital reading techniques to measure the water temperature inside.

You can attach it by removing the protective cover and stick it. It is also possible to switch easily between Celsius and Fahrenheit by using the single switch.

It is not necessary to completely submerge it inside the water, but it is made up of a tough outer shell; it is also water-resistant.

The LR1130 battery is included for better battery power so you may get a long-lasting life.


  • Attached with protective covers
  • Ideal choice for humidity readings
  • Able to read in both Celsius and Fahrenheit


  • Short battery life

8. RISEPRO Digital Water Thermometer For Fish Tank

It is perfect for taking a temperature reading, which offers efficient performance. It is easy to set up the thermometer by just mounting the display kit in the aquarium then put the sensor probe into the water. It is an excellent digital thermometer that comes with an LCD display, so it may be easy to read.

Arctic Silver 5 Thermal Paste

RISEPRO Aquarium Thermometer

  • Brand: RISEPRO
  • Type: Digital thermometer
  • Height: 2.3 x 0.6 inches
  • Weight: 3.4 ounces
  • Color: Black

This thermometer works efficiently in any tank. It also has easy to read the display when attempting to read the temperature inside the tank.

You can get readings either in Celsius or Fahrenheit, and it is highly durable so that it will provide long-lasting performance.

This equipment is ultimately designed with high-quality materials that can prevent the water from damaging the entire tank.

The RISEPRO Digital Water Thermometer comes with a replaceable battery, so the fish in the water will not get shocked if something is plugged into the tank.

The maximum range of temperature can be -58 degree F to +158 degree F; it is the best adaptable thermometer that can work better with various kinds of fish tanks and water.

If you use this thermometer at the marine water, freshwater, or tap water, it will give an exact temperature reading.


  • Simple to install
  • Good battery life
  • Comes with extra batteries


  • Inconsistent reading

9. JW Pet Company Smarttemp Thermometer Aquarium

Are you searching for the smart aquarium thermometer? The JW Pet Thermometer is a perfect choice for you.

Arctic Silver 5 Thermal Paste

JW Pet Company Smarttemp Thermometer

  • Brand: JW Pet
  • Type: Floating thermometer
  • Height: 4 x 0.5 inches
  • Weight: 1.12 ounces
  • Color: White

It comes with a sleek and compact design and has a safe green area that shows an ideal range of temperature.

It also has a magnetic substance; this device goes into the fish tank, and the magnet moves outward to keep the Smarttemp in a perfect position.

This equipment does not use any suction cups, and it has a built-in large LCD display which tells whether it is minimum or maximum temperature with the click of a button you can easily switch between Celsius and Fahrenheit.

The display unit can be mounted to the outside of the tank using the magnet or suction cup.

The Fahrenheit is placed on the white screen background, and a green safe zone is situated at the center.

This thermometer is ultimately designed with high-quality materials, and unique design combines with a magnet.

It is the best high accuracy aquarium thermometer; the Smarttemp also offers a green safe zone that can denote the optimal temperature range.


  • Easy to move
  • Works well and quickly
  • High tech thermometer


  • Had red-light indicator issue

10. KollerCraft TOM Temp Alert Digital Thermometer

It is an advanced temperature reading device that can measure the readings very accurately and correctly; it is constructed with high-quality materials, so this device is durable and can last for a long time.

It is designed with some unique features like an alarm alert; it makes a sound when you change water temperature so you can keep your fish fresh and alive.

Arctic Silver 5 Thermal Paste

KollerCraft TOM Temp Alert Digital Thermometer

  • Brand: KollerCraft
  • Type: Digital thermometer
  • Size: 7.5 x 1.5 inches
  • Weight: 1.6 ounces
  • Color: Blue

The LED notifications can give you an alert of the water temperature, which is audible; also, it is better to use in both freshwater and marine water.

It is designed with suction cups so you can quickly fix it outside the fish tank; it also represents a low temperature of 75 degrees and a high temperature of 82 degrees.

The LCD display shows the temperature and alerts you if it goes beyond the expected range. This thermometer is attached to the 3-foot cord plastic probe so that you can attach the suction cup to the inside wall of your aquarium.

It weighs just 1.6 ounces and can be used for both freshwater and saltwater tanks. It is the best thermometer, which gives an exact reading, and it offers excellent performance with a lot of alert features for your fish safety.

It is very convenient and easy to use, even for beginners. It is also possible to cling the thermometer outwards the tank so you can get individual digital reading measurements to gauge the water temperature within.


  • Easy to read display
  • Includes audible warning
  • Exact temperature measurements


  • Not showing room temperature

How to Choose The Best Aquarium Thermometer?

Choosing the best aquarium thermometer is a tough task, especially if you don’t know about aquarium accessories.


Once you make the decision, you should check the thermostat, whether it is easy to install and use. No one wants to the thermometer that is complicated to operate. If the thermometer can be installed outside of the tank, then you should avoid these models. It isn’t very easy to install.


Generally, an aquarium thermometer classified into three types that are Stick-on LCD thermometer, Digital thermometer, and Floating or standing thermometer. You can decide which type of thermometer is perfect for your tank.


Everyone wants to buy the durable aquarium thermometer. It will help if you read the customer reviews before you make the purchase. You can find the best thermometer with positive customer comments and ratings.


Accuracy is another essential factor consider before you purchase the thermometer. Check whether the thermometer provides an accurate result. If the thermometer doesn’t give the exact results, it may affect your fish.

Temperature Range

The next thing is the aquarium thermometer’s temperature range. The best thermometer temperature range starts from +10 degrees celsius to +40 degrees celsius. Do not buy the thermometer with a small range.


The readable thermometer for the aquarium is important. If the thermometer has a bright display, without any confusion, you can choose it.

Which Is The Best Aquarium Thermometer

Aquarium thermometer generally classified into three types, that are Digital, Submersible, and Stick-on thermometer.

1. Digital aquarium thermometer

Are you looking for an unbreakable thermometer? Then the digital thermometer is a perfect choice. It is classified into two parts that are sensor probe and digital display.

The sensor probe able to move anywhere in the fish tank, and the digital display shows the temperature of the aquarium. If you would like to purchase the temporary thermometer, then you can pick this one.

When you need to check the tank temperature, you just put this probe into your tank. After finishing your process, you can easily remove it. The probe also classified into two different types that are fixed and wired probe.

Fixed Probe

It is also known as an instant-read thermometer. It is directly attached to a sensor probe so you can quickly identify by the meter. Put the probe into your tank.

The digital display will show the results within seconds. It is tiny in size, so it doesn’t take too much space to store.

Wired Probe

This probe is attached to the cord that allows you to set the probe into your tank. You can store this probe anywhere in your tank.

Some of the advanced probes come with an alarm. It will intimate you when your desired setting is changed.

Overall the digital thermometer available at a low price, and it delivers an accurate temperature.

2. Submersible thermometer

If you want the thermometer for a small tank, then you can choose these types of thermometer. It produces a more direct measurement of the temperature.

It is made from glass, which is more fragile when compared to the other models. It is one of the cheapest models which is available on the market.

But, you don’t get any advanced features along with it. It is not suitable for aggressive and boisterous fish.

It is not digital, so you have to read the measurement by using a small scale. Submersible thermometer classified into three types. That is Floating, Standing, and Suction cup thermometers.

Floating submersible thermometer floats on the water, and it does not work well. It quickly spins into the water.

If you have the plants and background decoration in the tank, then it is the ideal option for you.

The standing submersible thermometer is the heaviest one when compared to the other submersible models.

You can read the temperature through the front of the aquarium tank. If you have the larger aquarium tank, then you can purchase this thermometer.

The suction cup submersible thermometer is one of the best thermometers on the submersible list. It is attached to the suction cup, so wherever you want, you can place this thermometer.

3. Stick ON thermometer

It is also called LCD thermometers because it is attached to the LCD display. It is the last type of thermometer, which is mostly used in freshwater aquariums.

Place this thermometer on the outside of the aquarium. The notable point about this thermometer is you don’t place it direct sunlight, vents, and heaters.

Because it may affect the current temperature. It doesn’t provide accurate results when compared to the other models.

Wrapping Up!

An Aquarium thermometer is the most useful tool because it tells the temperature of the water. Every aquarium owner should use the best thermometer to check whether the temperature in the tank is best!

The products mentioned above can offer accurate temperature readings, which are essential for the fish in your aquarium. 

We hope so our article about the best aquarium thermometer was helpful for your purchase.

Kim Goodwin
About Kim Goodwin

Kim Goodwin holds a Master's in thermal engineering from the University of Rhode Island. At Thermo Gears, she reviews most equipment that uses thermal imaging technologies.