best aquarium options - submersible aquarium option

Best Aquarium Thermometer Options (Guide & Reviews)

Let’s establish the basics. You need a thermometer in your aquarium. Why? Water temperature can be the difference between life and death in your aquarium. Therefore, it makes sense you would want to understand your options for the best aquarium thermometer.

Heaters are helpful in regulating your tank’s temperature; however, their thermometers aren’t always 100% accurate. Using a separate, more reliable thermometer can help you track your fish tank’s temperature and avoid cooking your fish.

In this article, we’ll explore the best aquarium thermometer options.  Let’s get started.

Best Aquarium Thermometer Options:

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What is the best aquarium thermometer?

Our recommendation for the best aquarium thermometer is the Cooper Atkins DFP450W Digital Thermometer. It is a highly accurate probe-style thermometer that will beep once certain temperature conditions have been met. It is also waterproof so if you drop it in your tank, no harm! Aquarists report that it is extremely helpful for water changes because you can test the water going into your tank, as well as the water in your tank, to make sure everything is exactly how you want it to be.

Our Pick
Cooper Atkins-DFP450W Digital Pocket Thermometer, 4-5/8 in. L,multicolor
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What are the different types of aquarium thermometers?

There are three different types of thermometers commonly used for measuring the temperature inside aquariums: digital thermometer and probe, submersible, and sticker strips. 

1. Digital thermometer and probe

Digital thermometer and probes have two different components:

  • Sensor probe – Sits underwater to monitor the temperature. The probe can be moved anywhere inside the tank.
  • Digital display – Remains outside the water and displays the temperature of your aquarium. 

This design keeps the electronics out of your tank which, from a safety perspective, is smart. Keeps them nice and dry and functional.

If you want a thermometer that does not permanently sit in your aquarium, this is your best choice. You can check the temperature on demand with this set-up.

Within this category, there are two main designs: 

Fixed probe

Envision a meat thermometer or a candy thermometer. The thermometer display attaches directly to the sensor probe. To use, simply dip the probe into your aquarium and the temperature will be shown on the digital display within seconds.

Fixed-probe thermometers are small and easy to use, They take up very little space, meaning they’re not going to clutter your aquarium cabinet.

The two negatives we can think of is that fixed-probe thermometers must be held by hand. If you don’t hold it, it will likely fall to the bottom of your tank, frying the digital display. Additionally, you’re not going to get a constant read on the temperature, so you could miss fluctuations.

Wired probe

Similar concept to the fixed probe; however, the probe and temperature meter are separated (but attached by a cord). This means you can set up a probe permanently in your tank while the meter sits on the outside.

This is helpful because you have continuous temperature readings. Additionally, the probe can be placed anywhere in your aquarium, which means you can get the information but you can also hide the probe so you don’t have the visual interference. 

Some wired probes can sound an alarm if the temperature goes outside your desired range, helping you automate the monitoring process.

Submersible

Not surprisingly, submersible thermometers are designed to stay underwater in your tank. You can check the temperature by simply looking inside at the thermometer.

Similar to the wired probe, these thermometers take up space in your aquarium. You also want to be able to read them so they’re typically placed in visible locations. 

Submersible thermometers are typically some of the cheapest options available so they might be worth exploring if you’re on a budget. 

There are three different types of submersible thermometers: floating, standing, and suction cup. 

Floating

As you might guess, this thermometer floats. The idea behind this concept is that your thermometer takes up less space this way.

Good idea in theory, bad idea in practice. Water movement will cause the thermometer to spin which means you can’t read it if it has spun in the wrong direction. We recommend avoiding this style.

Standing

This submersible thermometer is weighted, allowing it to sink to the bottom of your aquarium and stay there. 

To read the temperature, all you need to do is look through the front of your aquarium. If your thermometer is in the front of your aquarium, it could be easy to read. However, if it is in the back, you’re going to be squinting to see the numbers.

Also, if you have nosy fish that like to poke around at the bottom of the tank (I see you, cichlids), they’re going to bump into your thermometer, guaranteed. It will spin around over time, meaning you have to reach into the bottom of your tank to spin it back around.

Suction Cup

Ok, so the first two options of submersible thermometers are kind of a mess. We don’t recommend them. But if you’re gravitating towards a submersible style, a suction cup thermometer is the best.

The suction cup solves the problem of the previous two options by keeping your thermometer in one place. 

Nano tank using best aquarium thermometer option - submersible with suction cup - that doesn't take up a lot of space

Hate suction cups? Some options use a magnet, while others hang from the edge of your aquarium. 

Sticker Strip

Sticker Strip thermometers are also known as LCD thermometers. LCD refers to the liquid crystal ink that changes color according to the temperature of your aquarium.

Simply peel a sticker, attach it to the front of your aquarium, and it will detect the temperature of your water through the glass.

In theory, super simple design and easy to read. In reality, these sticker strips are often wildly inaccurate. Most hobbyists agree that stick-on thermometers are not accurate. Friends don’t let friends use thermometer sticker strips. 

Do you need an aquarium thermometer?

Yes, we recommend using an aquarium thermometer. Warm water and cold water looks identical. It is impossible to glance at your aquarium and know it is running hot or cold. Similarly, it is impossible to visually see if your nitrites or nitrates are high. We need testing equipment to understand the parameters that are occurring in our tanks. 

That’s where your thermometer comes in. It allows you to confirm that the water inside your tank is the right temperature for your fish. Massive temperature fluctuations can kill a fish and temperature that is consistently outside of your fish’s preferred range will stress it over time. Aquarium thermometers help you get the conditions correct.

Digital versus Analog Aquarium Thermometers

Analog thermometers are the old-fashioned type where you need to match up the liquid with the temperature range. Unless you have perfect vision or your thermometer is very, very large, you’re probably going to be squinting.

With a digital thermometer, you can see the precise temperature in a second. A digital thermometer can provide an accurate reading to 0.1°F. 

There is no guessing – is it 74.5 or 75? You just read what’s on the display, and you’re done.

How to choose the best aquarium thermometer

Ease of Use and Installation

A thermometer has one job – read the temperature accurately. Ideally, you want to place it in your tank and start reading the temperature immediately.

Some digital thermometers may need a few extra steps, but these don’t tend to be complex.

Accuracy and Range

Your thermometer’s job is to analyze the temperature. That’s it.  

Accurate readings on digital thermometers should be within at least +/- 0.1°F. The more accurate, the better.

The range of temperature on the thermometer is also important. It needs to cover the range that you’re going to keep your tank. Most good thermometers cover a range from 50 degrees F (10 degrees C) to 104 degrees F (40 degrees C).

Durability

Thermometers aren’t pricey pieces of equipment. However, you also don’t want to be replacing them frequently.

You want something that is durable and consistently accurate. Look for long-lasting durable materials and a good battery life.

Also special note around glass thermometers – they can break. Try to purchase one that is high-quality glass if you go that route.

And if you buy a mercury thermometer, the quality of the glass is extra important. 

Leaking mercury into your tank will likely killall of your tank inhabitants. 

Temperature Readability

Don’t waste time squinting to read the temperature. Pick one that’s easy to read so you can quickly check the temperature. 

We find that thermometers with a probe and LCD temperature display are the easiest to read.

Pricing and Reviews

Lastly, you should read the online reviews of the aquarium thermometer you’re considering to get a sense of how accurate the temperature reading is and how durable the equipment will be overall.

Ratings can be a bit subjective, so the reviews will help guide you to the best aquarium thermometer for your tank.

Best Aquarium Thermometer Options:

Best Probe Thermometer:  Cooper Atkins DFP450W Digital

Our Pick
Cooper Atkins-DFP450W Digital Pocket Thermometer, 4-5/8 in. L,multicolor
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Although the Cooper Atkins Digital Pocket Thermometer is a chef’s thermometer, it is excellent for aquarium use.

The superpower of this option is that It’s 100% waterproof. It is rated at IPX7, which means it is suitable for accidental dunks or rinsing under running water but cannot be permanently submerged. If you accidentally dunk this thermometer in your tank, it will survive the experience. Less pressure on you when you’re checking the temp!

It is not an instant temperature reading; you will need to keep the probe of this thermometer in your tank for 5 seconds so be prepared for a small wait.

Features: 

  • Alarm sounds once a preset temperature is reached
  • Waterproof

Pros: 

  • Safe if accidentally dropped in tank
  • Accurate temperature readings
  • Helpful for water changes

Cons: 

  • Must be held for 5 seconds to get temperature
  • Doesn’t provide continuous temperature information

Best Aquarium Thermometer with Alarms:Inkbird ITC-308 Digital Temperature Controller – Thermostat

Best Aquarium Thermometer with Alarms:
Inkbird ITC-308 Digital Temperature Controller Thermostat
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This is not technically a thermometer, it’s a temperature controller  – meaning it monitors the temperature of your aquarium and then takes the necessary actions to correct the temperature to get it in the correct range. For example, if your aquarium is too hot, it can turn off your heater. Fancy, right? 

This option has a wide range of alarms such as high and low temperature alarms. It can also tell if the sensor probe fails so you don’t have an equipment failure that results in a lack of information that causes your tank to get wiped out. This capability is way beyond the scope of your typical thermometer.

Features: 

  • Temperature controller and thermometer capabilities
  • High / low temp alarm 
  • Sensor probe failure alarm
  • Waterproof temperature probe

Pros: 

  • Alarm system automates temperature monitoring
  • Temperature controller features automate ideal temperature maintenance

Cons: 

  • If heater or chiller fails, no detection from system
  • Not suitable out of the box for saltwater aquarium

Good Alternative: Zacro LCD Digital Aquarium Thermometer

Good Alternative:
Zacro LCD Digital Aquarium Thermometer for Fish Tank
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This option has a large LCD display, which is attached to a submersible probe. The LCD Display has a suction cup, so you can easily attach it to the outside of your tank for simple monitoriing.

The size of the LCD display makes it very easy to read. 

This option displays temperature measurements within 0.1 degrees Farenheit.

Features: 

  • Suction cup on large, easy-to-read LCD screen; 
  • Displays Celsius or Fahrenheit temperatures
  • Battery-powered

Pros: 

  • Easy to use and install
  • Affordable
  • Battery life can be extended by turning off thermometer when not in use

Cons:

  • Some users report less accurate readings after extended time periods
  • No alarm capability

Good Alternative: RISEPRO Digital Water Thermometer

Good Alternative
RISEPRO Aquarium Thermometer, Digital Water Thermometer for Fish Tanks
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This is another digital thermometer option with an easy-to-read LCD display and a submersible sensor probe for accurate temperature readings.

This option has 2 suction cups for stronger attachment to your tank.

You can switch between Celsius and Fahrenheit. This unit has a large temperature range from -58.0 to 158.0 degrees Fahrenheit.

Features: 

  • Two suction cups for extra secure attachment to your tank
  • Battery powered

Pros: 

  • Comes with extra battery
  • Easy-to-read LCD

Cons: 

  • Difficult to read at night
  • No temperature alarms
  • Some users report inaccurate temperatures

Best Submersible: JW Smart Temp Thermometer for Aquariums 

Best Submersible
JW Pet Smart Temp Thermometer Aquarium
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A problem with many submersible glass thermometers is that they’re difficult to read. JW Smarttemp improves this by using a plastic backing with large printed numbers. So it might not be as visually appealing as glass but it is more functional for its actual purpose.

It uses magnets instead of suction cups. To me, magnets are a more visually appealing option so it makes up some ground there.

The magnet also made the thermometer easy to move around, a bonus when cleaning the aquarium. 

Features: 

  • Uses magnets for anchoring
  • Plastic construction
  • Has both Celsius and Farenheit readings

Pros: 

  • Easy to move around
  • Affordable
  • Magnets are clever way to mount thermometer

Cons: 

  • Some users report thermometer is about 2 degrees off
  • Works best on small tanks only

Best Thermometer Strip: American Thermal Aquarium Thermometer

Best Thermometer Strip:
American Thermal LCD Aquarium Thermometer
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Although we don’t recommend the thermometer strips in general, if you’re going to go that route, we recommend this option. 

The American Thermal thermometer uses sensitive, color-changing liquid crystals that respond to your tank’s temperature. For aquarium sticker strips,

they’re clear and easy to read.

Install is a breeze – simply peel and stick. This thermometer strrip can be removed and repositioned without losing a ton of stickiness, making it more durable. If you choose this type of thermometer, we recommend complimenting it with a more accurate thermometer with a digital display.

Features: 

  • Uses Fahrenheit 
  • Easy to instal
  • Measures 3 inches long by 1 inch wide

Pros: 

  • Affordable
  • Easy-to-read

Cons:

  • Less accurate than probe style thermometers 

Aquarium Thermometer FAQs 

Are stick-on aquarium thermometers accurate?

Stick-on aquarium thermometers are more accurate than dipping your finger into the aquarium water and guessing at the temp. However, they tend to measure the temperature of the glass, rather than the temperature of the water, so they’re usually off by a few degrees. That might not sound like a lot, but given how narrow some fish’s temperature requirements are, a few degrees could easily put you out of the ideal range. For this reason, we recommend simultaneously using a digital probe thermometer with your stick-on thermometer, since probe thermometers are typically the most accurate.

Where is the best place to put a thermometer in a fish tank?

There are three factors to consider in placing your thermometer: gravel line, heater location, and direct sunlight. Place your thermometer above the gravel line as you’re trying to measure the water temperature, not the gravel or substrate temperature. Place the thermometer inside the aquarium on the opposite side of the heater. Water near the heater will likely read higher than the actual temperature. Additionally, try to place your thermometer out of the path of direct sunlight as that will artificially increase the reported temperature.

Can you use a regular thermometer in a fish tank?

No, we don’t recommend using a regular thermometer in a fish tank. Most older human thermometers have liquid mercury inside of them, which is deadly to fish if the thermometer were to break. They’re also manufactured for human temperature ranges which aren’t ideal for fish, unless you’re looking to cook them. Additionally, most human thermometers are glass, which is fragile and presents another hazard to fish. Finally, the metal tip on thermometers is not meant to be submerged in water.

How do you put an aquarium thermometer in?

Installation depends on the type of aquarium thermometer. For example, for a thermometer sticker strip, clean the outside of the fish tank with glass cleaner on a lint-free cloth. It is recommended to install the strip in a location that will be easy to read. Peel the adhesive backing off the thermometer strip. Place the thermometer strip where you want it and press it against the glass. Rub over the strip with a credit card or identification card to smooth out any air bubbles.

For a probe thermometer, place the probe inside the tank where you want it to be. Choose a location that is away from the heater, above the gravel line, and out of direct sunlight. Mount the digital display in an easy-to-read location using the suction cups.

Conclusion

Aquarium thermometers are a requirement for your tank. Keeping track of the temperature is important for healthy plant and animal life. Thankfully, aquarium thermometers are not expensive pieces of equipment and there a few design options to maintain the aesthetics of your tank. They’re super simple to set up and they’re typically a breeze to clean.

Our all-around recommendation for the best aquarium thermometer is the Cooper Atkins DFP450W Digital Thermometer. It is a highly accurate probe-style thermometer than will beep once certain temperature conditions have been met. It is also waterproof so if you drop it in your tank, no harm! It will meet the needs of the most aquarium hobbyists.

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