The 10 Best Aquarium Thermometers

Here’s the deal:

Aquarium thermometers are important to make sure that the water in your tank is at the best level for your fish.

Thermometers can also help you track and solve problems if the water temperature is fluctuating throughout the day.

This guide will help you to choose the best aquarium thermometers for your tanks.

Contents show

The 10 Best Aquarium Thermometers

1. JW Pet Company Smarttemp Thermometer


This stands up stick thermometer gives a high accuracy reading. It holds on to the aquarium wall by a magnet instead of a suction cup. This gives it a stronger hold than a suction cup would. The thermometer has readings in Fahrenheit and Celsius and has a green zone to indicate optimal temperatures for the aquarium. It is simplistic in design but does exactly what you need it to do. With large, easy to read numbers and a great, affordable price range this thermometer is great for any home aquarium.


  • The magnet gives it more staying power than a suction cup.
  • Large numbers make this great for elderly or vision-impaired
  • It uses alcohol instead of mercury so it gives a faster temperature response


  • The magnet isn’t strong enough to work well on really thick glass.
  • The thermometer is not good in tanks with aggressive fish.
  • The thermometer is made of a lower quality plastic material.

2. LXSZRPH LCD Digital Aquarium Thermometer with Velcro


This is a high-quality digital aquarium thermometer with an alarm. This thermometer has a lot of features that make it easy to keep an aquarium’s temperature balanced. The thermometer features an LED light that flashes along with an alarm that sounds off if the aquarium temperature goes out of the high/low range that you set. It features a large digital display that makes it easy to read the temperature. The thermometer gives readings in both Celsius and Fahrenheit.


  • The thermometer has a one-year quality warranty in case it doesn’t work correctly.
  • The thermometer comes with accessories such as extra batteries and velcro.
  • The probe on the thermometer makes it possible to use it even in small fish bowls.


  • The thermostat isn’t waterproof so it has to be kept away from water.
  • All the functions and buttons could make it difficult to use the thermometer.
  • It is difficult to change the reading between Fahrenheit and Celsius.

3. American Thermal Liquid Crystal Aquarium Thermometer


This is a movable thermometer that you can stick on the outside of your aquarium. It gives readings in Celsius and Fahrenheit and has a horizontal design rather than a vertical design. This thermometer has a simplistic design but easily gives the temperature of your aquarium. The thermometer can give you the temperature at any level of your aquarium.


  • It is movable so it can be used in more than one spot or for more than one aquarium.
  • It’s easy to use and doesn’t have a lot of complicated buttons and features.
  • The thermometer is easy to read with a digital display.


  • This company doesn’t give a range of accuracy for this thermometer.
  • According to reviews, the accuracy can be inaccurate by 1 to 4 degrees.
  • This thermometer doesn’t come with any additional accessories or batteries.

4. Imagitarium Glass Thermometer


This is a stick thermometer that securely attaches to the inside of an aquarium using a suction cup that is included. The thermometer has a safety zone indicator marked on it in order to indicate the safe temperature zone for tropical fish. This thermometer gives temperature measurements in both Celsius and Fahrenheit.


  • The thermometer is made of glass, making it a very durable product.
  • The green safety zone indicator makes it easy to know if the aquarium water is at the right temperature.


  • This company doesn’t give a range of accuracy for this thermometer.
  • The numbers on the thermostat are small so this can make them difficult to read.
  • There isn’t a stated warranty on the thermometer.

5. DaToo Aquarium Thermometer


This blue digital thermometer boasts a simple and sleek design and does exactly what it is supposed to do–tell the temperature of the aquarium. The thermometer is completely waterproof so it can be completely submerged in the aquarium, giving it an extremely accurate temperature reading. It sticks to the aquarium by an included suction cup. The thermometer is so simple and easy to use that it doesn’t come with instructions. It also has a very wide range from low to high temperatures


  • The thermometer is waterproof so it is safe to submerge it in the aquarium.
  • The thermometer has a full, no questions asked one year warranty.
  • The simplistic design gives it one function–telling the water temperature–and it does this in real time with high accuracy.


  • For people who like a lot of features, this isn’t the best choice.
  • There isn’t a stated warranty on the thermometer.

6. Zacro LCD Digital Aquarium Thermometer


This digital thermometer features a probe that you submerge into the water to get the temperature reading. The thermometer has a very high accuracy–it is accurate to one-tenth of a degree. Although it doesn’t have a lot of features, it has the one you need the most and reads the temperature in both Fahrenheit and Celsius. The Zacro LCD Digital thermometer has an astounding 2 year warranty.


  • The thermometer has a 2 year warranty.
  • The thermometer has a very high level of accuracy.
  • It has a wide temperature range compared to other thermometers, from -50°C to +70°C.


  • It doesn’t have any other functions besides telling the tB01G7FAJG6emperature.
  • Although it does have an expansive temperature range, the operating temperature range is much smaller, from -10°C to +50°C.

7. SunGrow Betta Sticker Thermometer


This thermometer is a sticker–simply peel the paper backing and stick the thermometer on your fish tank. It is advertised as a Betta thermometer but can generally tell the temperature of the water with any type of fish in it. The sticker has color coding to easily alert you to the temperature of the tank. It is black with white letters and numbers that are large and easy to read. The simplistic design–simply peel and stick–makes this ideal for anyone to use, even children.


  • It is very simple and easy to use with no set up involved.
  • The blue color-coding makes it easy to tell the temperature of the tank.
  • The colors and large font make it easy to read, even for the elderly or vision impaired.


  • This thermometer can be influenced by heaters, lights, or other outside elements so the temperature readings could be off.
  • The thermometer doesn’t have any type of listed warranty.
  • It’s not advertised as re-stickable so it can most likely only be used once and only for one tank.

8. IUME Indoor Aquarium LCD Digital Thermometer


This is a dual purpose thermometer that measures the temperature of the aquarium water as well as the indoor temperature. It displays these readings on a large, easy to read digital display. The thermometer is accurate within 1° and can be set to Celsius or Fahrenheit. The thermometer has adhesive tape on the back so it can stick to the outside of the aquarium.


  • The thermometer has a high level of accuracy compared to other thermometers.
  • The large LCD screen is easy to read, making it great for the elderly or vision impaired.
  • The colors and large font make it easy to read, even for the elderly or vision impaired.
  • The thermometer has a wide temperature range from -50°C to +70°C.
  • Displaying the temperature of the aquarium as well as the room eliminates the need for two different thermometers.


  • It uses adhesive backing that could possibly wear out.
  • The adhesive backing will most likely only be able to be used once on one aquarium.
  • It’s not advertised as re-stickable so it can most likely only be used once and only for one tank

9. Colori Digital Aquarium Thermometer


This thermometer sports a cool, round design and blue color. The digital display gives the temperature from a probe inserted into the water. The Colori Digital Aquarium thermometer has a high level of accuracy as well as the option to set a minimum and maximum temperature so you will be alerted if the temperature goes out of this range. The thermometer comes with three different mounting options for your convenience–suction cup, adhesive, or magnet.


  • The thermometer has a high level of accuracy compared to other thermometers.
  • Three different mounting options add flexibility to where and how the thermostat can be used.
  • The manufacturer offers an 18-month warranty for the thermostat.
  • The thermometer has a wide temperature range from -50°C to +70°C.


  • The thermostat is not suitable for aquariums that contain salt water.
  • The thermometer is not waterproof (only the probe is) so it must be kept away from water.

10. Pranovo 5 Pack Floating Thermometer


This waterproof floating thermometer is made of sealed glass so it is safe for your aquarium. The thermometer has a high level of accuracy and attaches to the aquarium glass with a suction cup. It has a green safety zone to indicate when the aquarium water is at the correct temperature. This thermometer comes in a pack of five so you will have extras as a backup or for other aquariums.


  • The thermometer has a high level of accuracy compared to other thermometers.
  • Sealed glass design makes it easy to clean and safe for aggressive fish.
  • It comes in a pack of five so you will have extra thermometers if needed.


  • The thermostat is small, making the numbers and letters small and hard to read.
  • The thermostat doesn’t have a wide range of temperatures–it only goes from 0°C to 40°C.
  • The manufacturer doesn’t have a stated warranty for this thermometer.

Aquarium Thermometer Buyer’s Guide

Do I need to purchase batteries for an aquarium thermometer?

Most thermometers come with at least one battery in the package. You could always buy extras. See the package details to find out which battery it uses.

Are thermometers safe for my fish?

Most thermometers are safe for fish. Some thermometers made with a lower-quality material such as a thin plastic could be damaged by aggressive fish.

Which type of thermometer is best?

The best thermometer will depend on your personal needs and wants.

What type of thermometer would be best for a kid to use?

A thermometer with a simple design and basic functioning could be easier for a kid to use.

What is the life expectancy of a thermometer?

This varies by manufacturer, type, and substance used to make the thermometer (alcohol or mercury).

What are the qualities of a good thermometer?

A good thermometer should have good visibility for the numbers, quick reaction time to changing temperatures, and a high level of accuracy.

What do I do if the alcohol or mercury leaks into my fish tank?

Since the chemicals in the thermometer could be toxic to your fish, do a 100% water change. Make sure you get all the glass or weighted balls out of the tank if the thermometer broke. If your thermometer contained mercury, be cautious because mercury is dangerous for humans also.

My aquarium has a heater. Will this affect my thermometer?

Some thermometers can be affected by a heat source or a powerful light that gives off heat. Try to position your thermostat away from the heat source or light.

How well do thermometers work outside of the aquarium?

If you use a thermometer that is designed to work outside the aquarium then it should work with high accuracy. Keep in mind that having thicker than usual glass can affect the temperature reading.

Does having extra functions mean that the thermometer is better than others?

Not necessarily. The extra functions just make the thermometer more useful.

Can I use a thermometer in a small fishbowl?

Yes. You may want to buy smaller-sized thermometers that fit better in/on a small bowl.

What is the red substance in my thermometer?

The red liquid is colored-alcohol. It is less toxic than mercury but evaporates faster.

What is the silver substance in my thermometer?

If the substance in a thermometer is silver, this is most likely mercury. Mercury is not widely used anymore because it can be irritating to the skin.

What are the silver balls at the bottom of my thermometer?

These are small metal balls that can sometimes be magnetic. In rare cases, it may be small dots of mercury.

Are thermometers safe for other pets besides fish?

The substances inside of a thermometer can be toxic so it is important to place the thermometer out of reach of other pets.

I don’t want to use batteries. Is there such a thing as an electric thermometer?

A digital thermometer could be considered electric since it uses thermoelectricity to gather readings, but there aren’t thermometers that plug into an electric source. This would be dangerous to put around a water tank.

Are expensive thermometers better?

Not necessarily. Many inexpensive thermometers work great.

Where can I buy an aquarium thermometer?

Most pet supply stores sell aquarium thermometers. You can also find amazing deals on many retail websites such as Amazon.

Are thermometers necessary for aquariums?

It is important to keep an aquarium at an optimal temperature to ensure your fish will thrive. A thermometer can alert you to any problems with the temperature so you can fix it before your fish get sick or die.

Do thermometers require a lot of maintenance?

Thermometers don’t require a lot of maintenance. You may need to change the battery from time to time.



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