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Whether you’re keeping goldfish, tropical fish, or invertebrates, it’s always a good idea to keep track of your water temperature. Even if you don’t need a tank heater, you still need to be able to monitor the temperature as one of the water parameters you check routinely. The temperature of your tank can have a direct impact on the health of the animals and plants in your tank, and temperature can be used in conjunction with treatments for injury and illness. There are a lot of thermometers on the market, though, and they range from simple to complex. Here are reviews covering the 10 best aquarium thermometers to help you wade through the thicket of thermometers to find the best one for your tank.

A Quick Comparison of Our Favorites

Image Product Details
Best Overall
Winner
capetsma Digital Touch Screen Fish Tank Thermometer capetsma Digital Touch Screen Fish Tank Thermometer
  • Oversized LCD display
  • Fully wireless
  • Accurate <1˚
  • Best Value
    Second place
    Marina Floating Thermometer with Suction Cup Marina Floating Thermometer with Suction Cup
  • Fully wireless
  • Mercury free
  • Requires no power source
  • Premium Choice
    Third place
    Gain Express Digital Combo pH & Temperature Meter Gain Express Digital Combo pH & Temperature Meter
  • Oversized backlit LCD display
  • Includes replaceable pH probe
  • Power-save mode
  • Inkbird Wireless Thermometer Smart Sensor with Data Logger Inkbird Wireless Thermometer Smart Sensor with Data Logger
  • Also measures humidity
  • Battery-powered
  • Modern appearance
  • Inkbird Wi-Fi Aquarium Dual Probe Thermometer Inkbird Wi-Fi Aquarium Dual Probe Thermometer
  • Temperature range of almost 300˚F
  • Dual probes
  • Wi-Fi accessibility
  • The 10 Best Aquarium Thermometers – Reviews 2021

    1. capetsma Digital Touch Screen Fish Tank ThermometerFish Aid Antibiotics Clindamycin

     

    Temperature Range: 32-158˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: Battery
    Price Range: $$
    Extras: Touchscreen display

    The best overall aquarium thermometer is the capetsma Digital Touch Screen Fish Tank Thermometer because of how functional and user-friendly it is. This thermometer features a big LCD display that measures 3.2 inches from corner to corner, making it easy to read the display, even from multiple feet away. The display is clear, so the thermometer will not block your view into your fish tank. The entire thermometer measures 3 inches by 3 inches and it is fully wireless, instead attaching to the outside of the tank and reading the temperature through the glass. It measures in Fahrenheit and Celsius and is accurate within less than 1˚. It has a temperature range setting that will cause the display to flash if the temperature leaves your set range.

    This thermometer does not work well with plastic or acrylic tanks. It also may be difficult to remove once attached to the glass, so make sure you know exactly where you want it before you stick it into place. It runs on battery power but includes one battery plus an extra with the purchase of the thermometer.

    Pros
    • Temperature range over 100˚F
    • Oversized LCD display
    • Clear display helps the thermometer blend into the background
    • Fully wireless
    • Battery-powered and includes extra battery
    • Accurate <1˚
    • Flashes when temperature is outside your set range
    Cons
    • Not effective for plastic or acrylic tanks
    • Difficult to remove once attached to glass

    2. Marina Floating Thermometer with Suction CupMarina Floating Thermometer

     

    Temperature Range: 32-120˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: NA
    Price Range: $
    Extras: None

    If you’re on a tight budget, the Marina Floating Thermometer with Suction Cup is a great pick. This old-school thermometer does not contain mercury but uses a red dyed alcohol solution to show you the temperature of your tank. It’s fully wireless and doesn’t require a power source to function, so it will still work if the electricity goes out or you don’t have batteries. It goes inside your tank and has a suction cup to hold it to the side of your tank, but it floats, so if the suction cup comes loose you won’t have to go fishing in your tank for it. It floats vertically, so using the suction cup is completely optional. This thermometer is around 4 inches tall but only measures approximately ½ inch around.

    It features a green range of temperatures that show you the safe ranges for most tropical fish, but this range isn’t accurate for all tropical fish or for cool water fish. Since this is a mercury-type thermometer, it can be difficult to read and should be looked at head-on to get an accurate reading.

    Pros
    • Temperature range of almost 100˚F
    • Budget friendly
    • Fully wireless
    • Mercury free
    • Requires no power source
    • Includes optional suction cup
    • Floats vertically
    Cons
    • Green range isn’t accurate for some tropical and most cool water fish
    • Difficult to read and numbers are small

    3. Gain Express Digital Combo pH & Temperature MeterGain Express Store

     

    Temperature Range: 23-140˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: Battery
    Price Range: $$$
    Extras: pH meter, power-saving mode

    The Gain Express Digital Combo pH & Temperature Meter is a premium-priced thermometer with the bonus of an accurate pH meter. This thermometer can be wall mounted, hung on the side of the tank, or mounted on a tripod, which is not included. The large display measures approximately 2 inches from corner to corner and the entire monitor measures 3.5 inches by 2.48 inches. The LCD display has a backlight that allows you to read it even in the dark, but it goes into power-saving mode after 5 minutes of not being in use to lengthen the battery life. The pH meter has multi-point calibration to give you the most accurate reading possible.

    While this thermometer can be used all the time, the manufacturer advises that the life of the probe will last longer if not kept underwater all the time, although the probe is replaceable. It comes with batteries to get you started but will require four AA batteries every 3 months or so.

    Pros
    • Temperature range over 100˚F
    • Oversized backlit LCD display
    • Power-save mode lengthens battery life
    • Includes replaceable pH probe
    • Battery-powered and includes first four batteries
    • Can be mounted three ways
    Cons
    • Manufacturer advises against continuous use
    • Requires four AA batteries
    • Premium price

    4. Inkbird Wireless Thermometer Smart Sensor with Data LoggerInkbird Wireless Thermometer

     

    Temperature Range: -40-140˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: Battery
    Price Range: $$$
    Extras: Bluetooth and Wi-Fi enabled with app access

    The Inkbird Wireless Thermometer Smart Sensor with Data Logger is a great thermometer with a wide range and smart features. This thermometer can measure from -40˚F to 140˚F and can also be used to measure humidity, which can be a handy feature if you’re caring for mystery snail eggs or other items that are outside the water but require high humidity. This sensor measures approximately 2.5 inches by 2.5 inches and features rounded edges, giving it a modern appearance. The sensor is waterproof and made to last while the monitor itself magnetizes outside the tank. It runs on batteries and is Bluetooth enabled, allowing you to transfer readings from the monitor to your app, which then allows you to download the information. The app is intelligent and allows you to view trends and histories in easy-to-understand formats.

    This thermometer includes two batteries to get you started, but you will need to replace it with batteries every few months, and potentially more frequently if kept in continuous use. There are multiple items required for full Bluetooth and Wi-Fi accessibility, so setup may be confusing.

    Pros
    • Temperature range of almost 200˚F
    • Also measures humidity
    • Battery-powered and includes first two batteries
    • Bluetooth and Wi-Fi accessibility
    • Features a smart app with downloadable data
    • Modern appearance
    Cons
    • Premium price
    • Requires batteries
    • Setup may be confusing
    • Additional parts may need to be purchased for full accessibility

    5. Inkbird Wi-Fi Aquarium Dual Probe ThermometerInkbird C929A Wi-Fi Aquarium Temperature

     

    Temperature Range: -40-212˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: Electric
    Price Range: $$$
    Extras: Built-in electrical plug, smart app access

    The Inkbird Wi-Fi Aquarium Dual Probe Thermometer requires an electrical outlet, but it has a built-in electrical plug, so you won’t lose access to an outlet when using this thermometer. It is able to be used in conjunction with a heater and it sends you a notification if the water temperature doesn’t reach your set temperature within a set amount of time. It includes two probes, so if one probe fails you will still have a backup in the water to safely monitor the temperature. This thermometer is Wi-Fi enabled and will send you a notification if the temperature difference between the two probes is greater than 5˚F.

    The included instructions with this device are somewhat confusing and it may be confusing to set everything up. This item is bulky and may cover other outlets due to its size.

    Pros
    • Temperature range of almost 300˚F
    • Designed to be used with a heater
    • Dual probes
    • Smart app receives notifications with issues
    • Wi-Fi accessibility
    Cons
    • Premium price
    • Confusing instructions
    • Bulky
    • Requires an electrical outlet

    6. JW Pet Company Smarttemp ThermometerJW Pet Company Smarttemp Thermometer

     

    Temperature Range: 30-104˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: NA
    Price Range: $
    Extras: Magnetic fastener

    The JW Pet Company Smarttemp Thermometer is a good option for a simple thermometer on a small budget. This mercury-style thermometer functions by being placed inside the tank and uses a unique magnetic fastener to hold it into place. This means you don’t have to worry with suction cups or fishing a thermometer out of the bottom of your tank. It has large numbers that are easy to read and has a green range marked for the ideal temperature range for tropical tanks.

    This thermometer is 7 inches tall, so it does take up quite a bit of space on the side of the tank. It is accurate within 1.5˚F, which is a larger fault range than most aquarium thermometers. The glass of this thermometer is somewhat delicate and may break easily with cleaning.

    Pros
    • Budget friendly
    • Requires no power source
    • Unique magnetic fastener
    • Large numbers are easy to read
    Cons
    • Very tall
    • Larger fault range than most thermometers
    • Glass may break easily

    7. HDE LCD Digital Aquarium Thermometer

    HDE LCD Digital Aquarium Thermometer

     

    Temperature Range: -7-120˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: Battery
    Price Range: $
    Extras: None

    The HDE LCD Digital Aquarium Thermometer is very easy to use and only requires you to hit the “on” button and put a probe into your tank. The LCD screen mounts outside your tank via a suction cup while the measurement probe suction cups inside the tank. It’s accurate within 0.1˚F and the LCD screen measures 2.5 inches by 1.5 inches.

    The LCD display on this thermometer is not backlit, so it may be difficult to see in dark rooms. This thermometer does not include the batteries needed to get you started and the necessary batteries are an unusual size, so you may have to special order them. This thermometer does not have any smart features, so if you run into calibration or display issues, it may be difficult to fix them.

    Pros
    • Compact display
    • Easy to use
    • Temperature range over 100˚F
    • Accurate within 0.1˚F
    Cons
    • LCD display is not backlit
    • Does not include batteries
    • Batteries are an unusual size and difficult to find
    • May be difficult to fix issues

    8. Shyfish LCD Digital Aquarium ThermometerShyfish LCD Digital Aquarium Thermometer

     

    Temperature Range: -4-180˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: Battery
    Price Range: $$
    Extras: Transparent screen, high and low temperature alarms

    The Shyfish LCD Digital Aquarium Thermometer is a modern-looking thermometer with a white body and clear screen that allows you to view your tank through it. This thermometer can measure tank temperature, room temperature, and room humidity levels, all at once. It’s accurate within 0.3˚F and measures approximately 3 inches by 5 inches. You are able to set high and low temperature ranges and the thermometer will alarm if the water temperature deviates from the set range.

    This thermometer does not include instructions, so it may be difficult to determine how to use it and changing out the batteries can be complicated as well. Once the batteries are in it, the thermometer is on all the time and does not have an on/off switch.

    Pros
    • Temperature range over 100˚F
    • Modern look with clear LCD display
    • Accurate within 0.3˚F
    • High and low temperature range alarms
    Cons
    • No instructions
    • May be difficult to change out the batteries
    • No on/off switch
    • LCD display is not backlit

    9. JLENOVEG 2 in 1 Fish Tank Thermometer with Large LCD DisplayJLENOVEG

     

    Temperature Range: Unclear
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: Battery
    Price Range: $$
    Extras: Reads ambient room temperature

    The JLENOVEG 2 in 1 Fish Tank Thermometer with Large LCD Display measures approximately 2.75 inches by 1.5 inches. It sticks directly to your aquarium glass and is wireless, instead measuring temperature through the glass. It is also able to determine the ambient temperature within the room.

    To change the F/C setting, it’s necessary to open the battery compartment and use a paper clip or other fine item to press the small button. It’s unclear what the full temperature range of this thermometer is and since it is wireless and does not directly measure the water’s temperature, it has a large margin of error of up to 5˚F. It does not provide any alert or notification of temperatures falling outside of a set range.

    Pros
    • Large display
    • Wireless
    • Measures ambient temperature
    Cons
    • F/C must be changed with a fine point item
    • Unclear what the full temperature range is
    • Large margin of error
    • No alerts or notification of temperature falling out of range

    10. Fluval EDGE Digital Aquarium ThermometerFluval EDGE Digital Aquarium Thermometer

     

    Temperature Range: 64-86˚F
    Unit(s) of Measurement: Fahrenheit, Celsius
    Power Source: NA
    Price Range: $
    Extras: None

    The Fluval EDGE Digital Aquarium Thermometer is a simple thermometer that is fully wireless and doesn’t require batteries or other power sources. It sticks to the outside of your tank and measures the temperature through the tank glass. It has marked measurements at varying intervals up the height of the thermometer and each interval has its own color block. Whichever color block is most brightly lit shows the tank temperature.

    Since this reads temperature through the side of the tank, it has a high margin of error. It also has a small measurement range that does not go much below tropical ranges. This thermometer is not truly digital and functions in a somewhat similar fashion to a mercury-type thermometer, except it lacks a fluid-filled tube. It can be difficult to read the temperature unless you are looking fully head-on at the thermometer.

    Pros
    • Wireless
    • Easy to use
    Cons
    • Very small temperature range
    • High margin of error
    • Not truly digital
    • Can be difficult to read
    • Measures in intervals and not by individual degrees

    Buyer’s Guide

    How to Choose the Right Thermometer for Your Aquarium

    What are Your Needs?

    Choosing the right thermometer for your aquarium will rely heavily on what exactly you need from your thermometer. If your aquarium is in a room that has large temperature swings or no heating and air, then having a thermometer that will alert you to water temperatures outside your preferred range may work better for you than a thermometer you have to routinely check for changes.

    What’s Your Preference?

    Some people prefer fully digital thermometers, while others prefer the old school mercury-type thermometers. Also, the aesthetic of your tank can help you choose a thermometer. If you have a heavily planted tank, for example, you may be able to better disguise an in-tank thermometer than you would be able to in a mostly open tank. Probes can be easy to disguise, but they usually are connected to a monitor or display that requires batteries or electricity.

    What’s Your Needed Range of Error?

    In tanks with sensitive plants and animals, you need a thermometer with a small margin of error. If you’re keeping hardy fish that are comfortable at multiple temperatures, like goldfish, then you can likely get away with a slightly less accurate thermometer than you would be able to if you’re keeping corals. A couple of degrees isn’t going to matter much to goldfish, but rapid temperature changes and wide ranges can be deadly to more sensitive creatures and plants.

    What Makes a Good Thermometer?
    • Accuracy: The more accurate a thermometer is, the more likely it is to be a high-quality item that’s built to last. Accuracy can be important, especially when you’re caring for delicate plants and animals.
    • Ease of Use: Thermometers range from Bluetooth and Wi-Fi enabled to something as simple as “hit the on button”. A thermometer being less complex or easier to use doesn’t make it inherently better than something more complex, but you do want to look for a thermometer that is user-friendly and won’t be so difficult to sue that it isn’t functional for you.
    • Functionality: Functionality involves accuracy and ease of use, but it also involves what it can do for you. Do you want to receive an alarm when the water temperature leaves your chosen range? Do you want a thermometer that doesn’t have a probe attachment because your turtle might try to eat it? Finding a thermometer that is the most functional for you and your aquarium setup will help you get the most out of your purchase.
    • Extras: Extras aren’t necessarily a good or bad thing, but they are often nice to have. Extras can be anything from bonus batteries, replacement parts, or access to apps that can help you get the most of out of your thermometer.

    Conclusion

    These reviews have covered the 10 best aquarium thermometers to help narrow your search and put together the many different types of thermometers available to you, along with their bonus features. For functionality and ease of use, the capetsma Digital Touch Screen Fish Tank Thermometer is the top pick. If you’re interested in a floating thermometer, try the Marina Floating Thermometer with Suction Cup, and for something on the premium side, check out the Gain Express Digital Combo pH & Temperature Meter. You’ve got lots of options to choose from!


    Featured image credit: nektofadeev, Shutterstock