Whether you love the undersea ambiance that an aquarium brings, or you simply love fish and want to make them a feature aspect of your home, one of the most important things you have to get right is the water temperature, otherwise your fish might not have safe conditions to live in.

From choosing the right aquarium tank to spending hours at your local pet store choosing which fish you want to make a part of your aquatic family, it can be super easy to overlook some of the most important aquarium components that will ensure optimum fish health and water quality – and that includes a thermometer.

Small but essential, if you don’t make sure that your aquarium’s water is at the correct temperature, then it can have a negative effect on both your fish and your aquatic plants. If the temperature strays too high or too low from the temperature of the water your fish are native to, then it could cause your water-loving pets to suffer, become distressed, or even worse. 

Never fear, though, because we’re here to help. Here at RiverTankSetup, we’ve taken it upon ourselves to cut through the vast sea (get it?) of thermometer options out there, in order to present you with a shortlist of the top aquarium thermometers currently available on the market. So, ready to achieve optimum water temperature regulation? Just read on.

Zacro LCD Digital Aquarium Thermometer

Simple to use, affordable and reliable – there’s a lot to love about the Zacro LCD Digital Aquarium Thermometer, and it just so happens to be our best overall pick, too.

Designed with convenience in mind, the Zacro LCD Digital Aquarium Thermometer doesn’t require much know-how to use, which makes it an ideal choice for everyone, including those that have never used an aquarium thermometer before. 

To use it, all you have to do is simply submerge the included probe directly into the water of your aquarium, leave it for a few moments, and then wait for the LCD screen to provide you with an accurate temperature reading. Unlike other types of thermometers on the market, this one from Zacro features a super long, waterproof chord that can be submerged deep into the aquarium, which will help to ensure the accuracy of the reading. 

What’s more, after you have submerged the probe directly into the water, you will be able to attach it to the LCD unit to the outside glass surface thanks to its included suction cup. Not only will this make reading the LCD display as easy as can be, but it will also help to prevent the probe from floating around and disturbing your fish, while also helping to further improve the overall accuracy. 

Not only that, but as soon as you have set this thermometer up, you’ll be able to enjoy constant usage. Both the probe and cord are entirely waterproof and designed to resist corrosion, water damage, and even the occasional fish nibble. So long as the battery has juice, you’ll be able to keep a constant record of the current temperature of your aquarium’s water and ensure optimum living conditions for your fish and plants. 

This thermometer even comes with an included battery in the purchase, which is excellent value for money and will mean that you can get it up and running as soon as you take it out of its box. Affordable and reliable, the Zacro LCD Digital Thermometer is definitely worth considering. 


  • Designed for constant use: The probe of this thermometer does not need to be removed from the water in-between uses, which means you’ll be able to enjoy constant readings.
  • LCD screen: The large LCD screen will display the temperature of the aquarium in a large, easy-to-read font.


  • Basic design: Simple design of this thermometer may not be ideal for larger aquariums. 

Aquaneat Digital Aquarium Thermometer

On the search for a high-quality thermometer that packs plenty of value, too? Look no further than the Aquaneat Digital Aquarium Thermometer. 

Combining premium performance with an affordable price point, the Aquaneat Digital Aquarium Thermometer is an ideal choice for anyone on the search for a digital thermometer that isn’t going to break the bank.

Offering plenty of versatility, the Digital Aquarium Thermometer is compatible for use in your aquarium and is suitable for a wide range of water types, including freshwater, saltwater, tap water, and even marine water. Plus, featuring a large LCD screen, you’ll be able to read the temperature measurements without any trouble at all.

As soon as you take it out of the box, all you will need to do is insert the probe directly into the water and use the suction cup to fasten it to the inside of the aquarium glass. Then, switch on the LCD display, and you’ll get a true and accurate reading in seconds. 

The Aquaneat Digital Aquarium Thermometer is also designed to withstand wide temperatures (from -50 degrees celsius to +70 degrees Celsius) and can be used constantly, so you won’t need to worry about constantly going to the trouble of removing the thermometer from the water in-between reads. All in all, it’s a fantastic choice for any aquarium owner that’s on a budget.


  • Suitable for multiple water types: Unlike other thermometers on the market, this budget-friendly thermometer is compatible with a range of different waters, including salt water, fresh water, and marine water. 
  • Quick-setup: This thermometer requires very little setup time, and features an easy-to-use LCD screen that will make turning it on and off a breeze.


  • The suction cup can pop off: Some users have found that the suction cup can sometimes weaken.

LCR Hallcrest A-1005

If you don’t want to go for a digital thermometer, then a liquid crystal thermometer is a great alternative to consider that won’t require batteries to work, and the LCR Hallcrest A-1005 Liquid Crystal Vertical Aquarium Thermometer is a bestseller. 

Featuring a liquid crystal thermometer design, the Hallcrest A-1005 Thermometer features heat-sensitive sensors that will be able to change color to indicate to you what the temperature of your aquarium is. 

The liquid crystals present within the strip of this innovative little thermometer will be able to accurately detect the accurate temperature of the water. Wondering how? Well, technically speaking, the liquid crystals held within the strip of this thermometer feature properties of both liquid and crystals, which means that the color will be able to change while measuring temperature. 

What’s more, unlike other liquid crystal thermometers, the LCR Hallcrest Liquid Crystal Vertical Aquarium Thermometer doesn’t need to be submerged within the water in order to take an accurate reading, as it has been designed to be stuck to the outside of your aquarium glass. This is super handy because it means that you’ll be able to clearly see the measurements on the thermometer without having to squint through the glass and water. 


  • Sticks to the outside of the aquarium: Unlike other liquid crystal thermometers, this one won’t need to be placed directly inside the aquarium, which will help you to read it more easily.
  • Changes color: Alongside the measurements running vertically down the stick, you’ll have the additional visual aid of changing colors. 


  • It may not be as accurate as a digital thermometer: Non-digital thermometers can sometimes provide inaccurate readings, which is something to keep in mind.

Marina Standing Thermometer

Last but not least, we have selected the Marina Standing Thermometer, which is a great option to consider for those that want to purchase a standing/floating thermometer. 

This standing aquarium thermometer from Marina is ideal for those looking for a low-maintenance and long-lasting thermometer that’s going to be able to provide accurate readings – time and time again. 

Requiring no installation or power source, the Marina Standing Thermometer is good to go as soon as it arrives on your doorstep. Simply take it out of its packaging and gently drop it into your aquarium, and it will settle gently on the floor of your aquarium without disturbing any of your fish pets.

What’s more, Marina has strategically designed this little thermometer to be able to stand upright while inside the aquarium, which will ensure that you’re able to take accurate readings as you’ll be able to easily read the measurements. Don’t let its little size fool you, either, because this thermometer is able to withstand water pressure without breaking or impacting its accuracy, even in medium-sized aquariums! 

On top of that, you also have the choice of choosing between either Celsius or Fahrenheit, and even features a safety zone area to help you know whether or not the temperature is right for your fish. Marina has really covered all bases – it’s certainly one to consider if you do not want a digital thermometer. 


  • Affordable: Excellent value for money – ideal for those on a budget.
  • Remains upright: To help you accurately take recordings, this standing thermometer is able to remain upright once it has sunk to the bottom of your aquarium floor. 


  • Hard to read: Some users find that, though the readings are accurate, the thermometer can be difficult to read due to its little size.

Best Fish Tank Thermometers – Buyers Guide


One of the most important things that you should consider when selecting an aquarium thermometer is how accurate the thermometer is. Even though a thermometer might come with a whole host of fancy features, if it’s not going to be able to give you an accurate reading, then you’ll be wasting your money.

Even if the thermometer is only a few degrees celsius off the true temperature of the aquarium’s water, it can still have a negative impact on your fish and their wellbeing. Therefore, it’s extremely important to make sure that the thermometer you select will be able to provide you with accurate readings, time and time again.


You’re likely going to be using your thermometer multiple times daily, so it’s important to make sure that it’s easy and simple to use, otherwise, you might find checking the temperature difficult and tedious. All of the aquarium thermometers that we have recommended to you above pack plenty of functional features and ease of use, however, if you are planning to shortlist some additional options elsewhere, you’ll want to try and keep in mind that the more convenient a thermometer is, the easier you will find it to use.

In addition to this, you should also consider how easy it is to actually read the display screen. If you struggle to read small numbers, or you simply don’t want to have to go to the trouble of squinting every time you want to take a record of the aquarium’s temperature, then we recommend going with a digital thermometer. This is because these types of thermometers often come with a digital LCD screen that will be able to display the temperature in large font. 


Seeing as you’re going to need to submerge at least part of your thermometer inside the water of your aquarium, you’ll need to make sure that it is going to be durable enough to withstand any corrosion from the filtration system, as well as being able to withstand the water pressure without any changes to its performance, especially if you have a particularly large tank.

Though it should go without saying that your thermometer will be designed to be waterproof, we strongly recommend making sure that you thoroughly read the manufacturer’s instructions prior to use, as oftentimes only parts of a thermometer are designed to be able to withstand prolonged exposure to water. 

As an example, if you were using a digital thermometer and you submerged the digital display screen into the tank, not only would you cause the screen to break, but you could also cause the battery to become damaged and leak, which could be fatal if your fish accidentally ingested any of the battery acids.

For these reasons, it’s not only important to ensure that the thermometer you are purchasing is durable and going to be able to offer you a long service life, but you should also make sure that you’re aware of which parts are allowed to be submerged safely within the water – and which parts aren’t! 

Power Source

Believe it or not, another super important factor that you should take into account prior to purchasing a thermometer is what type of power mode it requires. All digital thermometers are often powered by an alkaline battery while floating thermometers often do not need to be powered by anything at all.

As far as accuracy goes, digital thermometers are often your best bet, however, it might be worth keeping a stick-on or floating thermometer in your spare drawer in an emergency, as you’ll be able to use one as a backup if you temporarily run out of batteries. 

Frequently Asked Questions

Are stick-on aquarium thermometers accurate?

Stick-on thermometers generally do provide accurate readings, although they are pretty well-known for sometimes providing readings that are a few degrees off the mark. More often than not, this isn’t usually a problem for standard thermometers designed for room use, though it shouldn’t go overlooked when used specifically for an aquarium.

Even if a temperature reading is only a few degrees off from the true temperature, this can still cause fish to become distressed and negatively affected, so we recommend considering going with a digital thermometer as your primary choice. Stick-on and floating thermometers are ideal as a backup option, and you should always ensure that you take their readings with a pinch of salt.

What’s more, stick-on and floating thermometers can be pretty difficult to properly read, while digital thermometers tend to feature large LCD display screens that are able to present the temperature clearly – so there’s no room for mistakes.

Where is the best place to put a thermometer in an aquarium?

Ideally, one of the best places that you should aim to keep your thermometer in an aquarium is right above the gravel line. This will ensure that you get the most accurate readings possible.

However, if you haven’t purchased a digital thermometer or stick-on thermometer, then a floating thermometer will need to be submerged directly into the aquarium, where you should position it opposite the heater. If you were to position it anywhere else, then you might discover that the readings are coming out a little too high, due to the thermometer being positioned in close proximity to the heater.