Last Updated on April 25, 2023 by Coral Realm

Aquarium thermometers are one of those small devices that are often overlooked, with so many to choose from and a wide range of prices, it can be hard to find one suitable for your fish tank. Thermometers are actually a vital piece of equipment, alongside a filter and lighting, to have when setting up a new aquarium for your beloved fish; they record the temperature of the water and allow you to check up on the water conditions with a quick look at the thermometer. 

But why do you need a thermometer if you know you have an aquarium heater

Heaters are needed to warm up the water to the setting you change it to, many beginner fish owners believe that this is enough. However this temperature needs to be steadily maintained, particularly if you have sensitive fish that will react badly to a sudden change in temperature. Thermometers are there to tell you the temperature at all times, meaning if the heater breaks and the water becomes cold, you will instantly know. 

Thousands of different thermometers are put up for sale on various different sites, making it difficult to navigate through to find yourself a reliable and inexpensive option. In this article we will discuss the different types of thermometers that are available, and what particular ones we recommend for you and your aquarium. Not tracking the temperature of the water will induce stress in the fish if fluctuations are not spotted quickly. If you’re looking for the Best salt water Aquarium Thermometer, we have a specific article on that. 


Best Aquarium Thermometer List

What types of Thermometers are there?

There are three types of aquarium thermometers: the stick on strip, the floating thermometer, and the digital thermometer. We find that the digital thermometers are the most accurate, with the floating thermometers following closely behind. Below we have listed the types you can find, where you can see which one is the best option for you. 

Stick on strip aquarium thermometer:

Stick on thermometers, also known as LCD (Liquid Crystal Display) thermometers, are the most affordable and simplest form of thermometer, they are often sold as part of a full aquarium set up pack. They do what they’re named after and are stuck onto the outside of the aquarium so you can read the strip easily.  

These strips are not digital, even though they are displayed with digits, they are simple to read with both Celsius and Fahrenheit readings, however some only come with Celsius scales in a bigger font. Stick on thermometers are pretty popular with fish owners who are new to the industry, they are relatively accurate enough for a general use and are really easy to use. The range of temperatures on these thermometers varies throughout the models, however they all usually have a high and low enough number to tell whether something is wrong.

There are definitely some negative debates on these thermometers, as they can be affected by the room temperature, due to them being stuck on the outside of the tank. If the room is much warmer or cooler than the tank water, it may affect the thermometers reading; they could also be affected by how thick the glass is between the thermometer and the water, many aquarists question whether these stick on thermometers are entirely reliable. They are also hard to read in low light as they are black in colour. 

When using these thermometers, make sure they are not in direct sunlight or near any object that will affect their reading, such as a heater or air conditioning vent. Make sure you stick them on the outside of the glass near the top of the water, placing them near the gravel may affect their reading due to the water flow 

These thermometers are more suitable for a general use rather than someone wanting a constant specific reading of an exact degree. These can be useful for community tanks to have a gage of the water temperature, for aquariums housing a special species that has specific temperature requirements, we recommend scrolling down to take a look at the digital thermometers. 

Floating aquarium thermometer:

Floating, or standing, thermometers are placed inside the aquarium and submerged in the water, making them slightly more accurate than the stick on strips as they cannot be affected by any outside elements. They have an attached suction cup so that they can be stuck onto the front of the aquarium and kept in place, the numbers are on a white background so they are easily read from the outside. Some models are designed to float around the aquarium, however ones sold with a suction cup are much easier to quickly glance at and read the temperature, rather than search around the aquarium for the floating one. 

This thermometer is submerged in the water, and the red line rises until it hits the temperature that the water is at. The numbers are pretty small and need to be read up close in order to see what the temperature is. These thermometers are also great for a general use as they have a green colored section that tells you the rough temperature an aquarium should be at, some also have red warning sections where the temperature is too high for the average aquarium. 

These are useful for community aquariums that house hardy fish such as guppies, as it gives you an indication of whether the water temperature is safe or not. Some species of fish require much warmer or cooler temperatures as others, so these floating thermometers can confuse you if the red line reaches the warning side of the thermometer. However, they will still give you a pretty accurate temperature of the water, regarding that you know what temperature your fish requires.  

The biggest problem about these thermometers that cause some aquarists to worry, is that they are made of glass. Even though they are unlikely to break, it can happen; and can result in small pieces of glass floating around the aquarium. If this happens, proceed with a full water change. These thermometers are not suitable for aquariums housing large aggressive fish as they may bump into the thermometer and cause it to break. It’s also not best for Thermometers in salt water tanks. 

Large aquariums may need more than one of these thermometers due to their small size, but this shouldn’t be a problem due to their cheap price!

Digital aquarium thermometer:

Digital thermometers are the most accurate but also the most expensive type of thermometer. These thermometers consist of an LED screen that is left outside of the aquarium and is attached to a waterproof wire, fitted with a probe at the end, that is placed into the water. This probe can be placed anywhere in the aquarium, some are fitted to a suction cup that allows you to leave it in one place on the side of the tank. Some types of digital thermometers connect wirelessly to the probe without a wire. 

Most digital thermometers require batteries, whereas some higher end types can be plugged into a socket. 

They have a digital screen that displays the exact temperature, down to the decimal point. The more advanced types allow you to turn on an alert that gives you a warning when the temperature gets too high or too low defending on the temperature that you have set it to. This is a great way to know straight away if the temperature is not correct. 

As the probe is fully submerged in the water, they are much more accurate than the stick on strip thermometers, and the fact that they are digital makes them an even better option than the floating thermometers. They are a great option for sensitive fish that need a specific high or low temperature, as it is much more accurate than the other types, as well as having a fitted warning system.  

Best Aquarium Thermometer Reviews

Best Aquarium Thermometer Reviews

Here are some thermometers that could be an option for your aquarium, including some of which we use ourselves:

1. VIVOSUN LCD Digital Aquarium Thermometer 

VIVOSUN LCD Digital Aquarium Thermometer
  • High Accuracy: Temperature Range: -50℃ ~ +70℃ (-58 °F ~ +158 °F); This aquarium thermometer is accurate to +/- 1℃, no matter whether the probe is placed in any corner of this fish tank, an accurate temperature will be displayed
  • LCD Display: Comes with a large LCD display that is easy to read clearly and accurately
  • Adjustable Unit Tempature: Easy to adjust the temp between Fahrenheit and Celsius displays; Long-press the power button to adjust the unit display
  • Two Suction Cups: Equipped with two suction cups, one for attaching the cable to the side of the tank and another for attaching the thermometer
  • Super Long Cable: The cable length connected to the probe is 78.74 inch (2 m) superior to 23.62 inch (60 cm) standard cable length; Allows accurate temperature measurements in even the largest fish tanks

This thermometer is a digital version with a LCD display that is easy to read on the screen. This is an accurate thermometer that would be great for small to medium sized aquariums to avoid buying more than one. 

The thermometer that holds the screen is 2.28” in length, 0.47” in width and 1.54” in height. It has a large range of temperatures from -50℃ – 70℃ (-58 °F to 158 °F), it includes a small button that changes the reading from Fahrenheit to Celsius and vice versa, depending on which you prefer. 

This thermometer comes with two suction cups on both the probes and behind the screen. This is great as it allows you to stick the thermometer onto the front of the tank to avoid having to search for it if it drops off the top. The probe can then be placed anywhere in the tank. The cable is 2 meters (78.74”) long which gives you more space to separate the probe to the thermometer. 

2. Capetsma Digital Touch Screen Aquarium Thermometer

Capetsma Digital Touch Screen Aquarium Thermometer
  • 🐌🐌 Cordless & Touch Screen Design : no probes or messy wires in water and backside temperature sensor stick on the outside glass of...
  • 🐌🐌 Large numbers on 3.2" Large Transparent Screen : 3.2" large glass screen is larger than most of the thermometers, large temperature...
  • 🐌🐌 Accurate Display : With an accurate temperature sensor stick on the surface of the fish tank, this Digital aquarium thermometer...
  • 🐌🐌 Easy to Operate : pull down the black battery cover below the screen, insert the battery, close it, stick and read the tank...

This digital thermometer is a slightly more expensive type, however still affordable, it is a cordless and touch screen thermometer with a unique transparent screen. As this is wireless it looks neat and tidy on the side of an aquarium. This thermometer is actually placed on the outside of the glass, unlike other wireless thermometers that have to be submerged. This thermometer is 3” x 3”, with a depth of 0.28”, a decent size for a medium to large aquarium, it may look slightly big on the side of a small tank, however it will still give you an accurate reading. 

Having this thermometer on the outside of an aquarium prevents any large aggressive fish knocking it off the size of the glass, the transparent screen will also prevent the thermometer from blocking any views into the aquarium. This thermometer is very accurate with the ability to change from Celsius to Fahrenheit depending on what you prefer. It has a large temperature range from 32°F to 158°F (0°C to 70°C) , it is battery operated that is easily accessible by quickly removing the cover below the screen to reveal the battery. 

You can also set a high and low temperature on this thermometer, so that there is a warning when the temperature gets to your set numbers. This is ideal if you want your aquarium at a particular temperature and you need to be notified when this changes. 

3. Jansamn Strip Aquarium Thermometer

Jansamn Brewing Aquarium Thermometer Strip
  • 【 Displays Degree Centigrade Fahrenheit 】 The thermometer strip has a range of 39℉ to 97℉ and 4℃ to 36℃. The large numbers are Fahrenheit and the small numbers are Centigrade
  • 【 Easy To Stick On 】 Simply pulled the backing off to reveal the adhesive back and applied to the front of your fish tank/aquarium/carboy/jar/fermentation bucket. Great way to keep a quick eye on your fish tank/wine jar/kombucha temp
  • 【 Easy To Read 】 The thermometer strip is a piece of temperature-sensitive paper. The colored marking shows the current temperature. If shows multi-color, please choose the average value
  • 【Kindly Tips 】 The best kombucha brew temp is 78℉ to 85℉. Keep your betta’s water between 78℉ to 80℉. Thermometer strips are 5” long and 3/4” wide

This aquarium thermometer is also a stick on strip thermometer, however this is a larger version with both a Fahrenheit and Celsius scale. This thermometer has temperatures ranging from 39℉ to 97℉ (4℃ to 36℃), so it is great for all types of aquariums that require high, average or low temperatures. 

This thermometer comes in a pack of 4, which is great for its affordable price; this also allows you to have multiple strips around the aquarium, which is perfect for a large tank. If this is not needed, you then have three strips spare for when you need them!

It is easy to stick on simply by removing the backing to reveal the adhesive layer. 

4. Marina Floating Fish Tank Thermometer 

Marina Floating Thermometer for Betta Fish Tank with Suction Cup, Aquarium Thermometer, 11201A1
  • Easy to read floating aquarium thermometer with suction cups
  • Includes a safety zone indicator appropriate for most tropical fish
  • Equipped with suction cups to attach to the side of your fish tank
  • Ensures your aquarium is at the proper temperature
  • Thermometer is 4.25 inches tall

This is a floating thermometer fixed with a suction cup to attach it to the glass and keep it in one place. Complete with a simple design and an easily readable scale, this is an affordable thermometer great for a range of aquariums. 

This thermometer is to be fully submerged in water for an accurate reading and can be moved around the aquarium depending on where you want it. To get the best use from this thermometer, make sure it is upright at all times to avoid the liquid moving from the bottom of the tube, place it near the top of the water to avoid any temperature changes near the gravel affecting the reading. 

This thermometer includes a safety zone which is green in color which highlights the average temperature of most fish tanks. Don’t worry if the reading is above or below this zone if your fish require slightly warmer or cooler temperatures! 

5. JW Pet Company Smarttemp Aquarium Thermometer 

Marina Floating Thermometer with Suction Cup
  • We are proud to introduce the NEW SmartTemp Thermometer
  • This unique design combines a thermometer with a magnet
  • The Thermometer goes on the inside of the tank and the magnet goes on the outside to hold the SmartTemp firmly in place, no suction cups needed

This aquarium thermometer is a floating thermometer that is not digital. With a simple design, it is very easy to use and is placed onto the side of the tank using the magnet. The magnet is discrete and looks like part of the design, this prevents it from looking untidy. 

This thermometer also includes a green safety zone to indicate the best average temperature. It has both Fahrenheit and Celsius readings with bold black numbers that are easy to read, however they are not big enough to be read from far away. 

6. Fluval 2-in-1 Wireless Digital Aquarium Thermometer

Fluval 2-in-1 Digital Aquarium Thermometer
  • 2-in-1: Measures water & room temperature accurately within 10C/20 F
  • No probes or messy wires
  • Large LCD display simultaneously shows aquarium and ambient room temperatures
  • Thermometer for use in fresh and saltwater aquariums

This thermometer is a 2-in-1 that measures both the water and room temperature within 1°C. It is a wireless thermometer so there are no probes or wires going into the water. It is not waterproof so it shouldn’t be submerged in the water, instead it sits on the outside of the glass using the adhesive strip on the back. Ensure that the adhesive does not get dirty before attaching it to the glass as this may affect its strength, it may leave some sticky residue after removing it from the glass, but this can easily be cleaned off. 

It is suitable for both freshwater and saltwater aquariums, it has a large screen that displays both Fahrenheit and Celsius readings, however the screen may be hard to read in low light due to the grey background. The water temperature and room temperature are separated on two separate screens, and it states clearly which one is which. Displaying the room temperature as well as the water temperature is a great way to monitor how well your heater is warming up the water, as if the room the aquarium is in is cold, and the water is not much warmer, it could indicate that the heater is not working as well as it should. 

7. LCD Digital Wireless Aquarium Thermometer 

LCD Digital Waterproof Aquarium Thermometer with Suction Cup
  • 💦- 100% Waterproof : With Sealed Ring Design, Fischuel Aquarium Thermometer can completely submerge into the water, water temperature measurement is more accurate. ( Your Betta can also use it as a rest leaf.)
  • ✋- Suction Pad For Ease Of Placement : Just find the best spot in the fish tank, then attach the unit with the small suction pad which will keep the thermometer in place until removal is required.
  • 🐳- Extreamly Easy To Use : No instructions necessary. This is the simplest aquarium thermometer on the market with no buttons to operate.
  • 👊- Durable : Powered by a LR44 battery which is very long lasting and easy to replace.(Batteries included)

This digital thermometer is completely waterproof so it doesn’t include any wires or probes, it simply goes into the water and sticks to the side of the tank via a suction cup. This is a more aesthetically pleasing version of a digital thermometer as it is much more tidy without a long wire coming out of the water. It can be placed anywhere in the aquarium and two can be bought for a large aquarium to measure both ends of the tanks temperature, this can easily be done due to their low price. 

These can be a great thermometer for bettas as they love to lay on surfaces, they could be a substitute for one of their rest leaves, many betta owners have caught their bettas having a rest on the thermometer! 

This thermometer only has a Fahrenheit reading and no additional buttons to operate it, this is a completely simple type of digital thermometer making it extremely easy to use, and more accurate than a strip or floating thermometer. It is durable and comes fully set up with the required LR44 battery, these are long lasting and easy to replace. 

8. Small Thermal Crystal Aquarium Thermometer 

American Thermal Liquid Crystal Aquarium Thermometer Vertical Small
  • Know your aquarium's temperature at a glance
  • Easy-to-read and accurate thermometer mounts on outside of your aquarium
  • Unbreakable, non-corrosive, and non-toxic
  • Fahrenheit scale

This thermometer is a stick on strip thermometer that is much smaller in size than others, making it suitable for small aquariums housing one of a small group of fish. This small stick-on thermometer would be great for a betta tank or any tank with a small required temperature range. 

This thermometer is extremely easy to read and is non invasive to the tank due to its small size; it can also be easily removed if you wish to replace the thermometer. 

As this thermometer has a limited amount of temperatures displayed, it is not suitable for an aquarium needing an unusually high or low temperature. 

9. Shyfish LDC Digital Aquarium Thermometer 

Shyfish LCD Digital Aquarium Thermometer
  • Show clearly temperature: Pure transparent screen, You can read the temperature data clearly in the LCD screen. You can choose seither Fahrenheit or...
  • Accurate measurement:The high-precision temperature probe can be immersed in the water for a long time to truly measure the temperature of the fish...
  • Multifunctional measurement:Fish tank water temperature, room temperature, indoor humidity, three in one
  • Alarm function: Independently set high and low temperature thresholds, and automatically alarm when the threshold is exceeded.
  • Easy to use: Submerge probe into fish tank to measure water temperature (Submerge probe only, do not submerge thermometer in water)

This digital thermometer measures the water temperature, room temperature and humidity. It is placed outside of the water with its wire and probe submerged into the water. It is white in colour and has a flat, slick shape which will make your aquarium look particularly stylish!

This thermometer also has a transparent screen which makes it look expensive and makes your aquarium look more tidy. There are several settings, one of which you can change the Fahrenheit setting to Celsius. You can also set up an alarm system that notifies you when the water hits a certain temperature that you set it to, it does this by flashing a red light every 10 seconds when the temperature has exceeded the limit. 

10. Veanic Digital Aquarium Thermometer 

This is a pack of two digital thermometers with a very simple design and display screen. As there are two in this pack, it would suit a larger aquarium that requires more than one thermometer to get an accurate reading. These thermometers include a meter long wire that attaches to the probe, this allows plenty of space between the probe that is submerged in the water, and the thermometer screen on the outside of the tank.

These thermometers only display a Fahrenheit reading, and do not include any suction cups to keep them in place. However, suction cups can always be purchased separately for a cheap price if you wish to have these. They can be used in all types of aquariums including freshwater and saltwater, make sure there is not a long part of the wire floating in the water to prevent any big fish from getting tangled. They have a high temperature range from –58℉ to 158℉. 

A note on Saltwater Thermometers

When measuring the temperature in a saltwater tank, it is recommended to use a thermometer specifically designed for use in saltwater environments. This is because the salinity of the water in a saltwater tank can affect the accuracy of a thermometer designed for use in freshwater tanks.

Saltwater thermometers are typically made of materials that are more resistant to corrosion from the salt in the water. They may also have a different calibration or temperature range than freshwater thermometers to ensure accurate temperature readings in saltwater environments.

If you are using a thermometer designed for freshwater tanks in a saltwater tank, it is important to ensure that it is accurate for the specific range of temperatures found in your saltwater tank. You may also need to clean and maintain the thermometer more frequently to prevent corrosion and ensure accurate readings.


All fish need to be kept in a certain range of water temperature, whether it be average, slightly cooler or slightly warmer. To monitor these conditions a thermometer is needed to tell you exactly what temperature your fish are living in. with so many options to choose from, we hope we have narrowed down your search and given you a good insight on what type of thermometer you need. 

In general, digital thermometers are the best way to go to get a precise reading of the water temperature. Even though they are more expensive, in our eyes it is worth the money to protect your aquatic species. 

Out of the options we have listed, our personal favorites are the VIVOSUN Digital Thermometer for an affordable option with an attached probe, they are small yet easy to read with a very accurate temperature; we can always rely on these to be right.

For a wireless and nicer looking alternative, we enjoy using the Capetsma Digital Thermometer, with a unique transparent touch screen it’s a great way for an aquarium to look professional whilst giving you a reliable reading. 

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