The Best Aquarium Thermometers (Review) in 2021

Last Updated June 2, 2021

All aquarium knows know how important it is to keep consistent temperatures within aquarium tanks, and to ensure that the temperature falls within a range that is suitable for the type of aquatic life that you keep. Finding the right thermometer to monitor the aquatic environment within your tank can be tricky. There are so many types of thermometer available, from LCD digital screens and sensors to stick on strips with color readouts, knowing which is right for you can be difficult. But, our panel of pet experts and lovers of all things aquatic are here to help. They have developed a list of the best aquarium thermometers to help you make the right choice for you.

The Best Aquarium Thermometer


The Zacro LCD Digital Aquarium Thermometer gives accurate temperature readings of your aquarium environment to within 0.1 degree. The thermometer is easy to use, just submerge the probe into the water and attach the display unit to the side of your aquarium tank using the suction cup that is provided. The large LCD screen gives a clear reading, so you can provide the optimal environment for your fish.

Temperature range from -50 degree Celsius to +70 degree Celsius

Operating temperature from -10 degree Celsius to +50 degree Celsius

Requires LR44 button cell battery – which is included

Temperature readings accurate to within 0.1 degree

Large, easy to read LCD screen

  • Brand: Zacro
  • Model: FBA_ZDT1-AUX-1
  • Weight: 0.32 ounces


The Marina Floating Thermometer with Suction Cup is the ideal solution for aquarium owners that are looking for a thermometer that does not require a power source. The traditional style thermometer is easy to read and is attached to the inside of the aquarium tank with the suction cups that are provided. The thermometer includes a safety zone indicator for tropical fish, so you can see, at a glance, if your temperatures are outside the safe range for your aquatic life.

Temperature range from 0 degrees Celsius to +50 degrees Celsius

Safe Zone indicator from +21 degrees Celsius to +27 degrees Celsius

Easy to read display

Attaches to tank using two suction cups – which are included

  • Brand: Marina
  • Model: 11201A1
  • Weight: 0.8 ounces


If you prefer a thermometer that remains outside your aquarium tank, then consider the A-1005 Liquid Crystal Vertical Aquarium Thermometer by LCR Hallcrest. This simple and easy to read thermometer attaches to your aquarium using a sticky strip on its back. It can be mounted vertically or horizontally to give accurate readings. It can also be removed and repositioned without losing adhesiveness. The thermometer changes color to indicate the current temperature and temperature changes, making it easy to read from a distance.

Temperature range 66 degrees Fahrenheit to 84 degrees Fahrenheit

Color changing for easy temperature reading

Sticks to outside of aquarium tank with adhesive strip

Can be removed and repositioned easily

  • Brand: LCR Hallcrest
  • Model: A-1005
  • Weight: 3.2 ounces


Jansamn Brewing Aquarium Thermometer

Fish and other aquatic animals rely on their environment’s temperature. Fish, in particular, don’t regulate their internal body temperature through standard means like sweating. This means that any sudden or gradual temperature change can lead to the unfortune and untimely demise of your fish because they manage their body temperature through the water around them. There are a few breeds of fish that can manage their temperature internally, but it’s unlikely that you found one at your local pet store.

JANSAMN’s aquarium thermometer product is so great because it’s simple to use and completely user-friendly. The temperature of the aquarium is highlighted in a block color on the thermometer strip, and the strip will stay stuck to any aquarium unit that you have in your home. It’s even suitable to be placed on fishbowls, tanks, and fermentation buckets. If you can place an adhesive thermometer onto the surface, you can measure temperature with JANSAMN’s product.

Adhesive backing

Measures in Fahrenheit and Centigrade

Designed with betta fish in mind

Measure the temperature of any glass aquarium or container

Easy to read

  • Brand: JANSAMN
  • Model: N/A
  • Weight: 0.28 ounces


The JW Pet Company Smarttemp Thermometer Aquarium Accessory is an in-tank thermometer that is secured in place with a magnet. The thermometer goes inside the tank with the gauge facing the tank, a magnet is then placed on the outside of the tank and positioned opposite the magnetic area at the top of the thermometer. The thermometer included a colored area that indicates the optimal temperature range for your aquarium. The display is easy to read and marked of in one degree Celsius steps (two degrees in Fahrenheit).

Temperature available in both Celsius and Fahrenheit

Temperature range 0 degrees Celsius to +40 degrees Celsius (30 – 100 Fahrenheit)

Designed to work inside your aquarium – kept in place with a magnet

Easy to read with optimal temperature range color indicator

  • Brand: JW Pet
  • Model: 21600
  • Weight: 1.12 ounces


The Qooltek Digital LCD Thermometer Temperature Gauge measures temperature in Fahrenheit and has an accuracy of plus or minus 2 degrees Fahrenheit. The probe sits at the end of a long cable, meaning the temperature can be read remotely. The end of the probe can be placed inside the aquarium tank, while the large LCD display makes reading the temperature easy.

Temperature readings in Fahrenheit

Temperature range -58 degrees Fahrenheit to +199 degrees Fahrenheit

Reading accuracy correct to plus or minus 2 degrees

Probe is placed inside the aquarium while display is read remotely

Large LCD display allows for easy reading

  • Brand: Qooltek
  • Weight: 1.12 ounces


capetsma Reptile Thermometer

The Thermo-Hygrometer that Capetsma markets is a wonderful little device for any homeowner with an aquarium or terrarium in their home. The hook feature at the top of the device has an adhesive back; offering double the security for wherever you decide to fix the thermometer to. This Digital Thermometer is also battery operated and requires just 1 LR44 battery (one of these batteries is included with the product from the Capetsma store on Amazon).

Though this thermometer is marketed and designed for reptiles, there’s no reason that you couldn’t use this on your fish aquarium if you preferred. Capetsma’s Digital Thermometer measures humidity as well as overall temperature, giving you more accurate and informative readings than other basic fish tank thermometers on the market. There’s also a hidden switch at the back that will allow you to change between Fahrenheit and Celsius readings.

Hook and adhesive to fix to aquarium

Humidity and temperature display

Energy saving

Battery operated

High level of accuracy

  • Brand: Capetsma
  • Model: N/A
  • Weight: 1.45 punces


The General Tools AQ150 In and Out Aquarium Thermometer includes a waterproof probe that allows it to provide extremely accurate temperature readings. The thermometer memorizes minimum and maximum temperatures and has an alarm to indicate when the temperature falls outside of the optimal temperature range. The display shows temperatures in either Celsius or Fahrenheit and the digital LCD display is easy to read.

Displays temperature in either Celsius or Fahrenheit

Temperature range -50 degrees Celsius to +70 degrees Celsius (-58 to +158 degrees Fahrenheit)

Memorizes high / low temperatures

Includes alarm feature

Easy to read digital LCD display

  • Brand: General Tools
  • Model: AQ150
  • Weight: 3.04 ounces


The digital thermometer from KEYNICE is a highly accurate temperature sensor that is ideal for aquariums. The display can be flush mounted to most surfaces and is easy to read with a digital and visual display. The thermometer is powered by a USB connection and includes a 3ft cable. The sensor itself is rustproof and made from 100% stainless steel. The unit automatically updates readings every 2.5 seconds.

Displays temperature is Celsius or Fahrenheit

Available temperature range -50 degrees Celsius to +110 degrees Celsius (-58 – +230 degrees Fahrenheit)

Readings accurate to +/- one degree

Visual and digital LCD display

100% stainless steel temperature sensor

  • Brand: Keynice
  • Model: AP-185-USB
  • Weight: 3.2 ounces


The Instant Easy Read Adhesive Strip Liquid Crystal Stick On Thermometer by Prairie Essentials is simple and easy to use. It can be stuck to the outside of your aquarium, using the sticky back of the strip. It gives a clear indication of the temperature by turning the corresponding part of the scale red. It provides readings in both Celsius and Fahrenheit and provides immediate and continuous temperature readings.

Displays temperature in Celsius and Fahrenheit

Temperature range +14 degrees Celsius to +31 degrees Celsius (58 – 88 degrees Fahrenheit)

Easy to read red display

Provides continuous temperature measurement

Self-adhesive and moveable

  • Brand: Prairie Essentials
  • Model: LCT2PCK
  • Weight: 0.64 ounces

Best Aquarium Thermometer Buying Guide

Knowing which the best aquarium thermometers are is only part of the answer to buying one that is right for you. It is also important to know what to look for in an aquarium thermometer, what the benefits are of using one, and the different types of thermometer that are available. In this section of the guide we look at each of these in turn and explore some of the most frequently asked questions about aquarium thermometers.

fish tank thermometer

What to Consider When Buying Aquarium Thermometers

The key thing you need your thermometer to do is give you accurate temperature readings, so that you can maintain your tank at the optimal temperature for your aquatic life. To achieve this there are a few things that all thermometers need:

  • Easy to install and use

The more complex and complicated the thermometer is, the more likely it is to go wrong – either through human error or break down. All your thermometer needs to do is give clear and accurate temperature readings. So, ideally, you want one that you simply place in or on your tank and that is it. Of course, if you opt for an electronic thermometer, you need to introduce a power source and switch it on, but again it does not need to be complicated.

  • Accuracy

You need your thermometer to provide an accurate reading, some fish are very demanding, and just a small temperature change can have dramatic effects on their welfare. Ideally your thermometer should be accurate to within + / – one degrees Celsius.

  • Range

The temperature range of the thermometer is also important. Too small a range could mean that the type of environment you need for your aquatic life is not covered by the thermometer. Generally, the best thermometers have a range from at least +10 degrees Celsius to +40 degrees Celsius (50 – 104 degrees Fahrenheit). Having one with a greater range is helpful but avoid anything with a small range.

  • Durability

Durability is essential, as you need your thermometer to remain accurate over time. You also want a thermometer that is not going to fall apart. Loose parts, particularly on a thermometer that is inside the tank could be dangerous to your fish. For this reason, consider the materials carefully and avoid mercury, unless it is fully enclosed in a strong durable enclosure that is designed to be submerged in water. Pay the same level of attention to the fixtures and fittings that come with the thermometer.

  • Readability

A clear display is a must. If you are in any doubt about being able to accurately read a scale or understand a color change thermometer, then opt of an electronic one with a clear digital LCD display.

Benefits of Using Aquarium Thermometers

It is vital to be able to maintain the correct water temperature in your aquarium. Not doing so can be detrimental to all the aquatic life you have in the tank from fish to plants and other organisms. Given this it is important to be able to accurately monitor the temperature, so you can make adjustments quickly and easily. While your heater regulates the temperature of the tank, it is not always very accurate in its readouts. Having a separate thermometer allows you to have a safeguard, a way of checking the readings you are getting from your heater. If you don’t have a heater that gives temperature readings, then a thermostat is even more essential to the welfare of your aquarium environment.

Types of Aquarium Thermometers

There are several different types of aquarium thermometers available on the market, however, they can all be placed into one of three broad categories – digital, standing, and stick on.

  • Digital

Digital thermometers tend to be the more expensive, however, a good digital thermometer offers value for money because of its durability and accuracy. Generally, this type of thermometer consists of a probe and a digital display, most often connected by a wire. The display is powered by either batteries or mains power. Probes can either be placed in the water when you need to take a reading or left in the water continuously to monitor the water temperature. Often digital thermometers have alarms to warn you when the temperature is outside of its optimal range.

  • Standing

Standing or floating thermometers are submerged into the water of the aquarium. They are not digital and therefore require you to be able to accurately read a scale. Some include a colored area around the optimal temperature range to help you identify immediate problems. However, this range is pre-set, so if your aquatic life requires a different range it will be of little help. If you have a large tank you would need several of these thermometers to ensure that the water temperature is consistent throughout the tank.

  • Stick on

These thermometers are often sold as digital because of their clear number displays. However, they are not truly digital and because they stick to the exterior of the tank, they are the least accurate of the three types. Readings can be affected by ambient room temperature, heaters, air conditioning units, and even the sun coming through a window. If they are being used care should be taken with where they are placed, both in terms of the position in the room and the position on the tank. Stick on thermometers should not be placed below the gravel level of the tank, as this gives an inaccurate reading of the water temperature above the gravel.

Related Post: Aquarium LED Lighting

Best Aquarium Thermometer FAQ:

Q:  What is an aquarium thermometer?

A:  An aquarium thermometer is a thermometer that is designed to monitor the temperature of your aquarium tank, ensuring that it stays within the optimal range for the aquatic life that live within the tank. The materials used are designed to withstand being submerged in water and be harmless to the fish or are designed to give readings through glass and to stay in place without slipping or unsticking from their position.

Q:  How does an aquarium thermometer work?

A:  It works by measuring the temperature of the water, rather than of the air above the water or the ambient temperature outside the tank. Specific thermometers work differently, and the manufacturer’s guides should always be consulted when setting up a thermometer. This is especially important with digital thermometers that include memory and alarm functions. It is important that the display on any thermometer is easy to see, so ideally the display should be placed at eye level. This is particularly important with stick-on thermometers to reduce the risk of misreading the scale.

Related Post: Aquarium Pumps

Q:  What temperature should my aquarium water be?

A:  The ideal temperature of your aquarium depends on the type of fish you keep. For example, a common goldfish requires a range of between 65 and 68 degrees Fahrenheit, a Fancy Tail Goldfish prefers 65 – 72 degrees Fahrenheit, and the optimal range for tropical fish is 72 – 80 degrees Fahrenheit.

Related Post: Best Aquarium Heater

Q:  Are sudden changes in temperature harmful for my fish?

A:  Yes, sudden changes in temperature are harmful to your fish. If you do notice that your temperatures are not within their optimal range, you should not rush to change the temperature of the water. Add warm or cold water, depending on what is needed, gradually. This allows your fish to acclimatize and does not cause shock or sudden changes in metabolic rates.

Related Post: Best Aquarium Substrate

Our Top Pick

Our top pick for an aquarium thermometer is the Zacro LCD Digital Aquarium Thermometer. This digital thermometer gives accurate temperature readings of your aquarium environment to within 0.1 degree. The thermometer is easy to use, just submerge the probe into the water and attach the display unit to the side of your aquarium tank using the suction cup that is provided. The large LCD screen gives a clear reading, so you can provide the optimal environment for your fish.


  1. Aquarium Water Temperature, How Stuff Work
  2. Kali Wyrosdic, How to Take Care of Fish, PetMD
  3. Dr. Craig Morton, How to Take Care of Freshwater Fish, wikiHow
Jarrett Gilpin
Jarrett, the security officer, and Toxi, his vapor wake dog, work tirelessly to help keep students, teachers, and the public safe on the Notre Dame campus. To help Toxi remain focused, healthy, and happy in his stressful job, Jarret feeds him only top-quality foods and treats. Fun toys are also a must-have as even security dogs need to have some fun in their free time. Aside from protecting the public, Jarret also enjoys sharing his expertise on canine care and diet to help other dog owners keep their pets healthy and content.
The Best Aquarium LED Lighting (Review) in 2021
The Best Aquarium Water Test Kits (Review) in 2021
The Best Aquarium Pumps (Review) in 2021
The Best Aquarium Water Conditioners (Review) in 2021
The Best Aquarium Substrate (Review) in 2021
The Best Aquarium Chillers (Review) in 2021