The Best Aquarium Thermometers

Keeping fish isn’t as simple as just introducing them to their aquarium and hoping for the best. You need to closely monitor their water parameters, including temperature. That’s why an aquarium thermometer is an essential bit of kit. Even if your heater has a built-in thermometer, it’s wise to have a second, separate thermometer to hand, just in case the first isn’t accurate.

We reviewed dozens of aquarium thermometers to identify the best of the best. We considered various factors, including thermometer type, accuracy, ease of reading, durability, and what existing users are saying about them.

Top Pick
Buy Now
Cooper-Atkins Waterproof Reduced-Tip Digital Thermometer

Waterproof and highly accurate, this is the perfect thermometer for double-checking temperature readings.

buy now
$36.80 USD

While the Cooper-Atkins Waterproof Reduced-Tip Digital Thermometer might not be designed for aquarium use, it’s far more accurate than many so-called aquarium thermometers on the market. You can’t keep it in place full time, but it’s excellent for using once a day or a couple of times a week to double-check the accuracy of a cheaper aquarium thermometer that you keep in situ.

The 5 Top-Rated Aquarium Thermometers

Editor's PicksBrandRating
Best OverallCooper-Atkins Waterproof Reduced-Tip Digital Thermometer4.5
Runner UpFluval Wireless 2-in-1 Digital Thermometer
3.4
Best Budget BuyMarina Floating Thermometer with Suction Cup3.8
Best Digital Aquarium ThermometerZacro LCD Digital Aquarium Thermometer4.1
Best Adhesive Thermometer StripAmerican Thermal Horizontal Aquarium Thermometer4.2

*Ratings are from Amazon at the time of publication and can change

Our Top Pick: Cooper-Atkins Waterproof Reduced-Tip Digital Thermometer

We love the simplicity of the Cooper-Atkins Waterproof Reduced-Tip Digital Thermometer. All you need to do is turn it on, stick the tip in your aquarium, and it returns the temperature reading in less than six seconds. Although it isn’t made especially for use in fish tanks, the waterproof design means it can withstand splashes or even being accidentally dropped into your aquarium. It has a temperature range of between -40 to 450°F, which is far more than sufficient for any aquarium, and is accurate to within 2°F either way.

This handy thermometer comes with batteries included and has a totally battery life of around 500 hours, so it will be years before the battery needs replacing. It’s guaranteed by the manufacturer to be accurate for life so there’s no need for calibration and means it’s the perfect choice to test the accuracy of any other aquarium thermometers you might have. Priced at just under $30, it’s one of the most expensive aquarium thermometers out there, but it’s worth the cost for the accuracy and durability.

Cooper-Atkins Waterproof Reduced-Tip Digital Thermometer Key Features: 

  • Customizable temperature alarm
  • Switches off after 10 minutes idle to reserve battery life
  • Returns results quickly

Our Runner Up Pick: Fluval Wireless 2-in-1 Digital Thermometer

Runner Up
Buy Now
Fluval Wireless 2-in-1 Digital Thermometer

A digital aquarium thermometer with no need for probes or wires.

buy now
$14.21 USD

There’s no doubt that the Fluval Wireless 2-in-1 Digital Thermometer is a convenient choice. It’s designed to stick on the outside of the tank and give constant temperature readings on its large digital LCD display. In fact, it’s so convenient and easy to use that it would have got our top spot if it were just a little more accurate. Unfortunately, because it sticks on the outside of the tank, rather than the inside, and doesn’t feature any kind of probe, the temperature reading can be out by a few degrees. This is fine for fish who can happily live within a fairly wide water temperature range, but won’t cut it for fish that need to be kept at precise temperatures, with only a degree or two of leeway.

That said, as long as you have a second thermometer to occasionally check the accuracy of this one, Fluval Wireless 2-in-1 Digital Thermometer makes an excellent choice for day to day use, as you just need to glance over at your aquarium to notice any fluctuations. It also measures the ambient temperature of the room, which can be useful to know as your heater will need to work harder in a colder room to bring the water to the correct temperature. At $17, it’s not the cheapest model out there, but still fairly reasonably priced.

Fluval Wireless 2-in-1 Digital Thermometer Key Features: 

  • Easily switch between readings in Centigrade or Fahrenheit
  • Large easy-to-read display
  • Suitable for freshwater or saltwater tanks

Best Budget Pick: Marina Floating Thermometer

Best for Budget
Buy Now
Marina Floating Thermometer

This basic liquid-filled aquarium thermometer is simple yet effective.

buy now
$3.99 USD

You don’t need to spend a lot to get an effective aquarium thermometer. And, the Marina Floating Thermometer proves it. With a price tag of less than $3, you can probably find enough loose change between your couch cushions to purchase this liquid-filled thermometer. Although it’s capable of floating in your aquarium, it comes with a suction cup to keep it in place, if you’d prefer. Though it’s harder to read than a digital thermometer (you’ll need to get up close). It tends to be more accurate than some of the cheap digital thermometers on the market.

The main downside is that this thermometer is made from fairly thin glass that could shatter if you don’t treat it gently. However, for the low price, you can’t really go far wrong.

Marina Floating Thermometer Key Features: 

  • Gives accurate readings
  • Has a green “safety zone” indicator
  • No need for batteries

Best Digital Aquarium Thermometer: Zacro LCD Digital Aquarium Thermometer

Best Digital
Buy Now
Zacro LCD Digital Aquarium Thermometer

Proof you don’t have to break the bank to find an effective digital aquarium thermometer.

buy now
$6.99 USD

If you want a decent digital aquarium thermometer on a budget, the Zacro LCD Digital Aquarium Thermometer is well worth your consideration. Its clear LCD screen displays temperatures that are accurate to within +/-2°F. And, retailing at around $7, it isn’t unkind to your wallet, either! It has a probe on the end of a wire that you submerge into your aquarium. The display part of the unit comes with a suction cup so that you can attach it to the outside of your tank to keep it set up full time.

While the Zacro LCD Digital Aquarium Thermometer does tend to be accurate in most cases, we’ve come across a handful of users who’ve had issues with it displaying inaccurate readings. As such, we would recommend having a second thermometer you know is accurate (such as our top pick) that you can use occasionally to verify the temperature.

Zacro LCD Digital Aquarium Thermometer Key Features: 

  • Choose between readings in Centigrade or Fahrenheit
  • Easy to use
  • Battery included

Best Adhesive Thermometer Strip: American Thermal Horizontal Aquarium Thermometer

Best Adhesive
Buy Now
American Thermal Horizontal Aquarium Thermometer

American Thermal makes the best adhesive thermometer strip around.

buy now
$9.99 USD

Adhesive aquarium thermometer strips aren’t always known for their accuracy, but the American Thermal Horizontal Aquarium Thermometer is a decent choice. Sure, it won’t give you the same accuracy as a submersible model or a properly calibrated digital thermometer, but it tends to be accurate within a few degrees. Stick this LCD strip on the outside of your aquarium and check which number lights up. If it’s illuminated in green, this is the actual water temperature; if illuminated in red, the water is one degree lower than the displayed temperature; and if illuminated in violet, it’s one degree higher than the displayed temperature.

It isn’t necessarily the most intuitive thermometer out there, but once you learn what the colors mean, it’s easy to read. A single strip thermometer will set you back around $7, or you can buy a set of three for $10, which is a good choice if you have more than one aquarium or you might want a backup.

American Thermal Horizontal Aquarium Thermometer Key Features: 

  • Horizontal orientation
  • No batteries required
  • Movable

Who Should Buy an Aquarium Thermometer

Just like keeping your tank clean or feeding your fish each day, providing the correct water temperature for your aquatic critters is a vital part of fish keeping. While you could just trust your heating equipment to maintain the correct temperature, it’s wise to monitor it independently with an aquarium thermometer. As such, any one who keeps a fish tank should own at least one aquarium thermometer.

Top Pick
Buy Now
Cooper-Atkins Waterproof Reduced-Tip Digital Thermometer

Waterproof and highly accurate, this is the perfect thermometer for double-checking temperature readings.

buy now
$36.80 USD

Important Features to Consider

An aquarium thermometer should have a few important features. Here’s what to consider when selecting a thermometer for your aquarium:

  • Thermometer type. The three main types of aquarium thermometers are digital, liquid-filled, and adhesive. Digital thermometers usually have a probe that sits inside the water while the display unit sticks on the outside, though there are some exceptions. Liquid-filled aquarium thermometers are like old-style mercury bulb thermometers (expect filled with a less dangerous substance), they sit inside the tank and may float, sink, or come with a suction cup. Adhesive strip thermometers are thin, flexible strips that stick on the outside of the aquarium and give an approximate reading.
  • Accuracy. Many aquarium thermometers list the degree of accuracy with which they record temperatures. A quality aquarium thermometer should be accurate to within +/-2°F. Those with lower degrees of accuracy aren’t suitable for fish with very precise temperature requirements. It’s worth noting, however, that some models are less accurate than they claim to be, so it’s worth having a properly calibrated digital thermometer to check the accuracy of your aquarium thermometer.
  • Durability. A highly-durable aquarium thermometer might cost a little more but it will last longer. It’s especially important that liquid-filled models be sufficiently durable, as your fish could be harmed or killed if they shatter.
  • Power options. Digital aquarium thermometers require batteries, so you could get caught out if the battery dies and you don’t have a replacement to hand. Liquid-filled and adhesive strip thermometers don’t need batteries, so they’re good to have as a backup, even if you usually use a digital model.
  • Ease of reading. Aquarium thermometers with large LCD displays are the easiest to read, especially if you have poor eyesight. It can be tricky to see the exact reading on liquid-filled models, though you should be able to tell the temperature to within a degree or two. Adhesive strip models often use a system of varying colors to tell you the exact temperature, so you’ll need to read the instructions to learn what each color means.

Frequently Asked Questions

What is an aquarium thermometer and how does it work?

An aquarium thermometer is a device used to read the temperature of the water inside your fish tank. It’s important to know the water temperature, since fish have specific water temperature requirements to keep them healthy. Different types of aquarium thermometers work in different ways, but most either sit inside the aquarium to read the temperature or have a probe that sits in the water. However, some models measure the water temperature through the glass of your aquarium.

Where do you stick a thermometer in an aquarium?

The water temperature should be consistent throughout your aquarium, so it shouldn’t make a difference where you position your thermometer. That said, in large aquariums, it’s a good idea to have two thermometers, one at either end, to ensure the water is of an even temperature throughout the tank.

Are digital aquarium thermometers more accurate?

A reliable, properly calibrated thermometer is more accurate than other varieties, especially since it can tell you the water temperature to one decimal place. However, you can find some cheap digital thermometers that are quite inaccurate, so it varies.

What temperature should my fish tank be?

The correct temperature for your fish tank depends on the type of fish you’ll be keeping. Most tropical fish require water temperatures between 76 and 80°F, but some tropical species need slightly higher or lower temperatures. Goldfish prefer lower temperatures, usually 68 to 74°F for fancy varieties or slightly lower for single-tailed goldfish.

Other Aquarium Thermometers We Reviewed

Top Pick
Buy Now
Cooper-Atkins Waterproof Reduced-Tip Digital Thermometer

Waterproof and highly accurate, this is the perfect thermometer for double-checking temperature readings.

buy now
$36.80 USD

We looked at 20 other aquarium thermometers. Even though they didn’t make our 5 best aquarium thermometers list, they’re the best of the rest and each is still a great option for your fish tank. The information you’ll need to compare each one is included with the listing.

Digital Aquarium Thermometers

HDE Digital Aquarium Thermometer

HDE Digital Aquarium Thermometer

With a suction cup on both the probe and the body of the unit, this digital thermometer is easy to position for constant monitoring.

Key Features: 

  • Reads temperatures to one decimal place
  • Clear display
  • Battery included

Cost: $8

JCreate Fish Tank Thermometer

JCreate Fish Tank Thermometer

Simply stick this wireless thermometer on the outside of your tank, switch it on, and you’re good to go.

Key Features: 

  • Lets you set temperature parameters
  • Flashes when water temperature above or below set parameters
  • Simple to use

Cost: $17

Lifegard Aquatics Digital Temp Alert

Lifegard Aquatics Digital Temp Alert

This quality digital probe thermometer features an alarm that sounds if the water goes above or below a set range.

Key Features: 

  • Adjustable temperature range
  • AAA battery included
  • Large display is easy to read

Cost: $40

MarsAqua Digital Aquarium Thermometer

MarsAqua Digital Aquarium Thermometer

This compact digital probe thermometer is accurate to within +/-2°F.

Key Features: 

  • Large, clear temperature display
  • Simple operation
  • Takes temperatures to one decimal place

Cost: $7

VEE GEE Scientific Ultra High Accuracy Digital Thermometer

VEE GEE Scientific Ultra High Accuracy Digital Thermometer

While it isn’t designed as an aquarium thermometer, this scientific-grade option is highly accurate and great for checking if your permanently-positioned thermometers are correct.

Key Features: 

  • Perfect for spot readings
  • Returns results almost instantly
  • Lab quality

Cost: $22

Zoo Med Digital Thermometer

Zoo Med Digital Thermometer

Another digital option with a wired probe. Suction cup on the body lets you position it on the outside of the tank.

Key Features: 

  • Easy to switch between Fahrenheit and Centigrade
  • Clear LCD display
  • Simple to use

Cost: $5

Zoo Med Submersible Digital Nano Thermometer

Zoo Med Submersible Digital Nano Thermometer

A fully-submersible digital thermometer suitable for nano aquariums or even betta tanks.

Key Features: 

  • Discreet, compact design
  • Includes suction cup for easy positioning
  • Two batteries included (one spare)

Cost: $20

Adhesive Strip Aquarium Thermometers

American Thermal Instruments Small Vertical Aquarium Thermometer

American Thermal Instruments Small Vertical Aquarium Thermometer

This compact strip thermometer can read temperatures between 67 and 83°F.

Key Features: 

  • Easy to position
  • Clear display
  • Compact design great for small tanks

Cost: $6

American Thermal Instruments Vertical Aquarium Thermometer

American Thermal Instruments Vertical Aquarium Thermometer

A larger version of the option above and a vertical version of our top pick. This is an excellent option if you’re set on an adhesive strip thermometer.

Key Features: 

  • Temperature range between 65 and 85°F
  • Movable design
  • Accurate readings

Cost: $8

LCR Hallcrest Liquid Crystal Vertical Aquarium Thermometer

LCR Hallcrest Liquid Crystal Vertical Aquarium Thermometer

The movable design of this strip aquarium thermometer means you can reposition it if you don’t get it right the first time.

Key Features: 

  • Clear LCD display
  • Easy to use
  • Gives accurate results

Cost: $5

SUKRAGRAHA Traditional Stick-on Digital Temperature Thermometer

SUKRAGRAHA Traditional Stick-on Digital Temperature Thermometer

They don’t give quite as accurate results as pricier options, but the low cost is tempting, especially if you have a backup thermometer.

Key Features:

  • Shows temperatures in Fahrenheit and Centigrade simultaneously
  • Easy to read
  • Vertical orientation

Cost: $7 for 10 strips

TAAM Stick On Thermometer

Taam Stick On Thermometer

With its large, clear print, it;s easy to see the temperature reading on this thermometer, even from afar.

Key Features: 

  • Temperature range between 64 and 93°F
  • Simple to use
  • Effective adhesive

Cost: $8

Uxcell Plastic Fish Tank Thermometer Sticker

Uxcell Plastic Fish Tank Thermometer Sticker

We don’t have a lot of feedback about this newer brand but it’s an extremely affordable choice.

Key Features: 

  • Easy to position and use
  • Clear display
  • Reads temperatures between 64 and 93°F

Cost: $3

Liquid-Filled Aquarium Thermometers

Fluval Nano Thermometer

Fluval Nano Thermometer

The compact size of this thermometer means it doesn’t take up much room in your tank, but it’s also tricky to read.

Key Features: 

  • Temperature range of 35 to 125°F
  • Suction cup included
  • Great for small aquariums

Cost: $6

JW Pet Company Smart Temp Thermometer

JW Pet Company Smarttemp Thermometer

This in-tank liquid-filled thermometer comes in both standing and non-standing designs.

Key Features: 

  • Either has a standing design or magnetic fastening system
  • Easy to read
  • No need for a suction cup

Cost: $3 to $6

Mundopet Floating Thermometer

Mundopet Floating Thermometer

Although this thermometer is generally accurate, some buyers reported receiving defective models, so double-check it’s working properly before you set it up.

Key Features: 

  • Safe zone indicator
  • Floating design
  • Suction cup included

Cost: $6

Penn Plax Standing Thermometer

Penn Plax Standing Aquarium Thermometer

 

This stand liquid-filled aquarium thermometer sits at the bottom of the tank.

Key Features: 

  • Easy to read
  • Indicates safe zone
  • Sturdy design

Cost: $7

Penn Plax Floating Aquarium Thermometer

Penn Plax Floating Aquarium Thermometer

A floating version of the thermometer above that comes with a suction cup so you can attach it to the side of your tank for easier reading.

Key Features: 

  • Give accurate readings
  • Safe zone indicator
  • Stays in place effectively

Cost: $7

Pranovo 5 Pack Floating Thermometer

Pranovo 5 Pack Floating Thermometer

These aren’t the best liquid-filled aquarium thermometers out there, but the affordable multi-pack is great for anyone with several fish tanks.

Key Features: 

  • Floating design
  • Suction cup
  • Shows safe zone

Cost: $10 for a pack of five

TAAM Rio Aquarium and Pond Floating Thermometer

TAAM Rio Aquarium and Pond Floating Thermometer

This floating thermometer is great for large aquariums, or for indoor or outdoor ponds.

Key Features: 

  • Cord lets you easily pull it in to read temperature
  • Plastic casing for extra durability
  • Temperature range between 20 and 120°F

Cost: $15

Products You May Be Interested In:

Lauren Corona