Best Aquarium Thermometers (Review & Buying Guide) in 2019

All aquarium knows know how important it is to keep consistent temperatures within aquarium tanks, and to ensure that the temperature falls within a range that is suitable for the type of aquatic life that you keep. Finding the right thermometer to monitor the aquatic environment within your tank can be tricky. There are so many types of thermometer available, from LCD digital screens and sensors to stick on strips with color readouts, knowing which is right for you can be difficult. But, our panel of pet experts and lovers of all things aquatic are here to help. They have developed a list of the best aquarium thermometers to help you make the right choice for you.

best aquarium thermometers
Zacro LCD Digital Aquarium Thermometer

Zacro LCD Digital Aquarium Thermometer

General Tools AQ150 In and Out Aquarium Thermometer

General Tools AQ150 In and Out Thermometer

Marina Floating Thermometer with Suction Cup

Marina Floating Thermometer

Best Aquarium Thermometers Buying Guide & FAQ

Knowing which the best aquarium thermometers are is only part of the answer to buying one that is right for you. It is also important to know what to look for in an aquarium thermometer, what the benefits are of using one, and the different types of thermometer that are available. In this section of the guide we look at each of these in turn and explore some of the most frequently asked questions about aquarium thermometers.

aquarium thermometers for fish

What to Consider When Buying Aquarium Thermometers

The key thing you need your thermometer to do is give you accurate temperature readings, so that you can maintain your tank at the optimal temperature for your aquatic life. To achieve this there are a few things that all thermometers need:

  • Easy to install and use

The more complex and complicated the thermometer is, the more likely it is to go wrong – either through human error or break down. All your thermometer needs to do is give clear and accurate temperature readings. So, ideally, you want one that you simply place in or on your tank and that is it. Of course, if you opt for an electronic thermometer, you need to introduce a power source and switch it on, but again it does not need to be complicated.

  • Accuracy

You need your thermometer to provide an accurate reading, some fish are very demanding, and just a small temperature change can have dramatic effects on their welfare. Ideally your thermometer should be accurate to within + / – one degrees Celsius.

  • Range

The temperature range of the thermometer is also important. Too small a range could mean that the type of environment you need for your aquatic life is not covered by the thermometer. Generally, the best thermometers have a range from at least +10 degrees Celsius to +40 degrees Celsius (50 – 104 degrees Fahrenheit). Having one with a greater range is helpful but avoid anything with a small range.

  • Durability

Durability is essential, as you need your thermometer to remain accurate over time. You also want a thermometer that is not going to fall apart. Loose parts, particularly on a thermometer that is inside the tank could be dangerous to your fish. For this reason, consider the materials carefully and avoid mercury, unless it is fully enclosed in a strong durable enclosure that is designed to be submerged in water. Pay the same level of attention to the fixtures and fittings that come with the thermometer.

  • Readability

A clear display is a must. If you are in any doubt about being able to accurately read a scale or understand a color change thermometer, then opt of an electronic one with a clear digital LCD display.

Benefits of Using Aquarium Thermometers

It is vital to be able to maintain the correct water temperature in your aquarium. Not doing so can be detrimental to all the aquatic life you have in the tank from fish to plants and other organisms. Given this it is important to be able to accurately monitor the temperature, so you can make adjustments quickly and easily. While your heater regulates the temperature of the tank, it is not always very accurate in its readouts. Having a separate thermometer allows you to have a safeguard, a way of checking the readings you are getting from your heater. If you don’t have a heater that gives temperature readings, then a thermostat is even more essential to the welfare of your aquarium environment.

Types of Aquarium Thermometers

There are several different types of aquarium thermometers available on the market, however, they can all be placed into one of three broad categories – digital, standing, and stick on.

  • Digital

Digital thermometers tend to be the more expensive, however, a good digital thermometer offers value for money because of its durability and accuracy. Generally, this type of thermometer consists of a probe and a digital display, most often connected by a wire. The display is powered by either batteries or mains power. Probes can either be placed in the water when you need to take a reading or left in the water continuously to monitor the water temperature. Often digital thermometers have alarms to warn you when the temperature is outside of its optimal range.

  • Standing

Standing or floating thermometers are submerged into the water of the aquarium. They are not digital and therefore require you to be able to accurately read a scale. Some include a colored area around the optimal temperature range to help you identify immediate problems. However, this range is pre-set, so if your aquatic life requires a different range it will be of little help. If you have a large tank you would need several of these thermometers to ensure that the water temperature is consistent throughout the tank.

  • Stick on

These thermometers are often sold as digital because of their clear number displays. However, they are not truly digital and because they stick to the exterior of the tank, they are the least accurate of the three types. Readings can be affected by ambient room temperature, heaters, air conditioning units, and even the sun coming through a window. If they are being used care should be taken with where they are placed, both in terms of the position in the room and the position on the tank. Stick on thermometers should not be placed below the gravel level of the tank, as this gives an inaccurate reading of the water temperature above the gravel.

thermometers for aquariums

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Best Aquarium Thermometers FAQ

Q:  What is an aquarium thermometer?

A:  An aquarium thermometer is a thermometer that is designed to monitor the temperature of your aquarium tank, ensuring that it stays within the optimal range for the aquatic life that live within the tank. The materials used are designed to withstand being submerged in water and be harmless to the fish or are designed to give readings through glass and to stay in place without slipping or unsticking from their position.

Q:  How does an aquarium thermometer work?

A:  It works by measuring the temperature of the water, rather than of the air above the water or the ambient temperature outside the tank. Specific thermometers work differently, and the manufacturer’s guides should always be consulted when setting up a thermometer. This is especially important with digital thermometers that include memory and alarm functions. It is important that the display on any thermometer is easy to see, so ideally the display should be placed at eye level. This is particularly important with stick-on thermometers to reduce the risk of misreading the scale.

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Q:  What temperature should my aquarium water be?

A:  The ideal temperature of your aquarium depends on the type of fish you keep. For example, a common goldfish requires a range of between 65 and 68 degrees Fahrenheit, a Fancy Tail Goldfish prefers 65 – 72 degrees Fahrenheit, and the optimal range for tropical fish is 72 – 80 degrees Fahrenheit.

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Q:  Are sudden changes in temperature harmful for my fish?

A:  Yes, sudden changes in temperature are harmful to your fish. If you do notice that your temperatures are not within their optimal range, you should not rush to change the temperature of the water. Add warm or cold water, depending on what is needed, gradually. This allows your fish to acclimatize and does not cause shock or sudden changes in metabolic rates.

aquarium fishes thermometer

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Our Top Pick

Our top pick for an aquarium thermometer is the Zacro LCD Digital Aquarium Thermometer. This digital thermometer gives accurate temperature readings of your aquarium environment to within 0.1 degree. The thermometer is easy to use, just submerge the probe into the water and attach the display unit to the side of your aquarium tank using the suction cup that is provided. The large LCD screen gives a clear reading, so you can provide the optimal environment for your fish.


  1. Aquarium Water Temperature, How Stuff Work
  2. How to Take Care of Fish, PetMD
  3. How to Take Care of Freshwater Fish, wikiHow
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