Eight Most Accurate Aquarium Thermometers in 2018

If you’ve read through some of the pages of this site, you’ve probably read several times how crucial it is to maintain a stable temperature for your fish, and that temperature should be suited for the fish you have.

If you have a tropical fish or any marine life that needs warm water, then you’re going to need a heater for your aquarium. But how do you know your aquarium water has the right temperature? To get an accurate reading, you should get the most accurate aquarium thermometer available.

My recommended thermometer is the AODE, continue reading for more options.

Best aquarium thermometer

Types of Aquarium Thermometers

How to Use It


Top Fish Tank Thermometers Reviews

Here are some reviews of the best thermometers you can use:


1. TOOGOO Digital LCD Thermometer

Let’s start with a very affordable and basic digital thermometer like this one. It offers a 25mm X 12mm LCD screen, with a 1-meter cable connecting it to a probe.

It’s very compact and it’s smaller than your hand. It weighs just 3.5 ounces, so it doesn’t offer much weight when you install it using the suction base.

It’s powered by a DC 1.5V LR44 button battery which is included with your purchase.


  • It offers reasonably accurate readings. You can get your temperature readings in °C or °F.
  • It’s quite durable, so it won’t break when you accidentally drop it.
  • It’s cheap enough that you won’t have problems buying several for different parts of a very large tank.
  • The battery is included. To conserve power, you can turn off the display and just turn it on when you want to see the temperature.


  • As it’s cheap, you don’t get much in the way of features.
  • The LCD screen can be difficult to read. At night, you can’t read it at all until you turn on the room light.
  • There’s no power outlet option.

2. KollerCraft TOM Temp Alert Digital Thermometer for Aquariums

Now this is more expensive, but it offers a lot more features. It measures 7.5 x 5 x 1.5 inches and weighs just 1.6 ounces. This can be used for both freshwater and saltwater tanks.

The display shows you the temperature, and then it also warns you when it goes beyond the preset 75 to 82 degrees F.

The display also gives you the time of the alert, and you also get an audible warning. Also, there’s a memory feature that saves the high and low temperatures were.

The thermometer display is attached via a 3-foot cord to a plastic probe, which has a suction cup you can attach to the inside wall of your aquarium. It’s powered by batteries, which can be 2 Energizer 357 button cells or 2 LR 44 button cells.


  • You get a warning when the temperature reading goes outside the preset range.
  • The display is easy to read.
  • The temperature reading is very accurate.


  • You can’t change the preset.
  • There’s no plug.

3. Marina Floating Thermometer with Suction Cup

This one measures 4.25 inches tall, and it’s meant to “float” by sticking it to a wall inside the tank with the suction cup.

The temperature reading has a safety zone indicator so you can tell more easily if it goes outside the safe temperature range.


  • It’s very affordable.
  • It offers accurate readings.
  • It doesn’t need batteries.


  • Don’t use the suction cup on acrylic tanks, as it will leave ring stains that will prove very difficult to remove.
  • Its small size doesn’t make it easy to read the temperature reading.

4. American Thermal Horizontal Aquarium Thermometer

This thermometer measures 0.75" x 4.25" and weighs a puny 0.3 ounces. It’s designed to go outside the aquarium and below the waterline. You attach it horizontally by using the adhesive.

The back of the thermometer senses the temperature inside the aquarium through the glass, and then it shows a digital display of the temperature.


  • The adhesive uses liquid crystals, and they can be gently peeled and then you can put it on another location.
  • The temperature reading is very accurate for this sort of thermometer.
  • The temperature display is very easy to read.


  • You don’t get features like alerts, but then this is a more basic thermometer.

5. Fluval Nano Thermometer

This small glass thermometer is only 4 inches long. It offers a temperature range from 35° to 125° F.

No batteries needed at all, and all you need to do is to stick it on the outside of the tank with the suction cup.


  • This is quite small, so it won’t be too obtrusive for small tanks.
  • The suction cup works well.
  • It’s affordable.


  • It’s not quite as accurate as it ought to be.
  • Because of the wide range of the temperature, getting a precise read of the temperature isn’t easy either.

6. AODE Digital LCD Aquarium Thermometer

This battery-powered thermometer measures 2" x 1.25" while the 90 cm (3 feet) cable attaches to a probe which you submerge in the water.

It comes with a digital display that can switch from °C to °F. It can show the temperature from 70 °C (158 °F) to -50 °C (-58 °F).

It’s only powered by one LR44 button cell, which is included in the purchase.


  • Its temperature readings are very accurate, as it’s designed to stay within 1 °C.
  • The display is very large and easy to read.
  • To preserve the battery life, you can always just turn off the display.
  • The probe and suction are barely noticeable inside the tank.
  • It’s also very affordable


  • I wish there was a plug for this.

7. Lifegard Aquatics Digital Temp Alert

The Lifegard Aquatic “Big Digital” is exactly that – Big.

The super-size 4-inch by 4-inch temperature monitor has huge easy to read LCD characters.

This makes it easy to see the temperature from a distance.

The Big Digital Temp Alert has a programmable alarm that alerts you when the temperature is above or below the acceptable range.

The unit displays both aquarium water temperature and the room temperature.

The thermometer has a probe that measures the aquarium water and an internal thermometer that measures the room temperature.

The in-tank probe has a suction cup for attaching it to the aquarium glass. These two measurements are displayed on the LCD screen.

A red LED indicates when the temperature is out of range. There are four temperature alert options:

  • High Temp Alert Only (Probe).
  • Both High & Low Temp Alert Only (Air/Room).
  • Low Temp Alert Only (Probe).
  • Both High & Low Temp Alert Only (Probe).

The Lifegard Aquatic Big Digital can be used in freshwater or saltwater aquariums. The unit can be attached to the aquarium glass or stand alone.

It is powered by one AAA battery which is included.


  • LED alarm.
  • ​Easy to read LCD screen.
  • Measures aquarium and room temperature.


  • LED display would be easier to read in the dark.

8. Keynice Digital Thermometer

The Keynice Digital Thermometer is a unique thermometer designed for many temperature monitoring applications including aquariums.

This temperature monitor is not designed specifically for aquarium use.

It must be powered by a USB power source. This could be a phone charger or a computer.

Keep in mind that there is no data monitoring. The USB cable is only for supplying power to the unit.

The back-lit color LCD display shows a sweep pattern that displays temperature in Fahrenheit or Celsius. A switch on the back of the display unit allows you to select F or C readout.

The temperature probe is made of stainless steel and the manufacturer says it is saltwater-safe. The display box is small, measuring 1.9 inches x 1.1 inches. The temperature range is 58 °F to 230 °F.


  • Unique design.


  • Must be powered by USB.
  • No high or low temperature alarms.
  • Display unit cannot be easily mounted to the aquarium.
  • No battery power option.
  • No data monitoring despite USB connection.

My Pick

I really don’t like having to stick anything to my glass tanks, and suction cups and adhesives are even more problematic when you have an acrylic tank. This is why I use a digital monitor. And when it comes to digital monitors, I always recommend the AODE.

It doesn’t have the alarm feature, but that’s okay. That can be more trouble than it’s worth, especially when you can’t adjust the preset temperature range. With the AODE, you get the most important features in a thermometer: affordable, accurate, and easy to use.

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