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Types of Aquarium Thermometers

Every Aquarium needs a thermometer. They’re not just an instrument used to tell the temperature of a room or location, they’re also crucial for the health and safety of your fish. Different types of aquarium thermometers can be purchased at most pet shops and are available in manual and automatic options.

What are these options? Let’s take a look at each type to better understand their uses and applications.

What is an aquarium thermometer and do you need one?

To understand the different types of aquarium thermometers, it’s important to realise why they need to be used. Thermometers are used so you can monitor the temperature of the water in your tank. It is important to keep the temperature of reef tanks at a desirable level to keep your fish healthy. There are different requirements for the temperature of fresh and saltwater tanks.

How do you place an aquarium thermometer?

You can place a thermometer either on the outside of the aquarium glass or inside the tank using suction cups. It is important to keep your thermometers out of direct sunlight as this can affect readings.

If placed on the outside of the glass, make sure it is out of reach from your fish. Keep in mind an aquarium thermometer is not a toy and should be kept away from children to prevent injury.

What are some factors that affect temperature of fish tanks?

There are many things that can affect the temperature of your tank including lighting, room temperature, usage of filter and the addition of live plants. Be sure to monitor your tank temperature on a regular basis as these changes can happen swiftly.

8 Best Aquarium Thermometers

Image Name of ProductFeaturesReviewsCHECK PRICE
Zacro LCD Digital Aquarium Thermometer- Submergible Probe with Suction Cup

-Large Easy to read LCD screen

-Temperature readings to within 0.1 degree

-Powered by one LR44 button cell (included)
4.6 from 6723 ratings
Capetsma Digital Touch Screen Fish Tank Stick on Aquarium Thermometer- Cordless & Touch Screen Design

-Large numbers on 3.2" Large Transparent Screen

-Accurate Display

-Suitable For Different Water Types
4.4 from 3153 ratings
Thermometer World Digital Aquarium Thermometer- Submergible Probe with Suction Cup

-Large Easy to read LCD screen

-Powered By 1xAAA battery. (included)
4.3 from 1002 ratings
JW Pet Company Aquarium Thermometer- In-tank thermometer is secured with magnet outside the tank

- No suction cups needed

- Green safe zone indicates optimal temperature range

-Large easy to read numbers
4.4 from 1,991 ratings
JW Pet Company Standing Aquarium Thermometer-Weighted aquarium thermometer

-Fits securely in gravel

-Unique anchoring fins Will not shift positions

-Green safe zone indicates optimal temperature range
4.4 from 1,991 ratings
Marina Floating Thermometer with Suction Cup-Easy to read floating aquarium thermometer with suction cups

-Includes a safety zone indicator appropriate for most tropical fish

-Equipped with suction cups to attach to the side of your fish tank

-4.25 inches tall
4.4 from 13,972 ratings
hygger Stick-on Digital Aquarium Thermometer- Cordless & Sticker Design

- Touch screen with built in alarm to alert major temp change

-Switch℃ and ℉ + Salt and Fresh water Compatible

-Replaceable button battery
4.8 from 12 ratings

Types of Aquarium Thermometers:

Typically you can find 3 types of thermometers in the market to measure the inside temperature of your aquarium. All of these have their own characteristics and some perform better than others.


Digital Aquarium thermometer and probe:

Digital thermometers are usually very accurate. You can place the probe in the water to measure the temperature or outside your tank as well. The outside option is recommended if you have a larger tank.

The Digital Aquarium thermometers have two different parts: sensor probe and digital display. The sensor probe can be placed either inside or outside the tank. A sensor probe is made of high quality stainless steel, and it is important to keep it away from sunlight as it affects the reading. 

A Digital Display is the second part of the thermometer. You can easily read aquarium temperatures with digital displays. These types of displays will usually be attached with a suction cup or clamp.

If you are looking for accuracy and precision then digital thermometers are recommended. Normally digital thermometers display in both Celsius and Fahrenheit. A digital aquarium thermometer can read the temperature with accuracy up to +/- 0.1 degrees.

A digital thermometer is your long-term friend as it is durable and can work up to 100 feet. You can obtain the reading of depth and surface water temperature by placing the meter on the desired location.

A disadvantage of the digital aquarium thermometer though is the price. They are generally more expensive than the analogue thermometers and also require frequent battery replacements.

However the best thing about digital thermometers is their reliability when it comes to taking temperatures. The accuracy of their measurements make it easy for you to manage and maintain your tank.

There are two different types of probe thermometers you will be able to choose from:

Fixed probe

Fixed Probes are also known as Instant Read Thermometers. These are simple meters that are directly attached with a sensor probe.

Simply dip the probe inside the tank and in a few seconds it will display the temperature of your fish tank on the digital display.

These fixed thermometers are best for small fish tanks, but can also be used in larger tanks.

One downside with a fixed probe though is you have to hold it while checking the temperature otherwise it will fall down into the aquarium.

Wired Probe

A wired probe has 2 separate parts and, as the name suggests, attached with a wire. You can dip this in the fish tank permanently and keep the digital meter outside the water to check the temperature at anytime.



Submersible aquarium thermometer

These are the most common type of thermometers used in an aquarium. The best brands have a high accuracy level and durable construction. Make sure you check to see if it is waterproof, as not all thermometers are . It’s also a good idea to get a digital model so there won’t be any confusion on what the temperature actually is.



Floating Aquarium Thermometer

These are the second most common type of thermometer in an aquarium. They use a mercury bulb to tell the temperature and they need to be in good condition because if they break they can release hazardous chemicals into your tank. Make sure to clean away any algae or other buildup on them, as this will cause inaccurate readings.


Standing submersible thermometer

This type can be placed inside or outside of the tank. Out of these two options, an external model is more suited for use as a primary thermometer since it’s easier to read and more accurate .

It also gives you a direct reading instead of having to look into the water where it might be distorted by what’s going on below. However, this model does not need to be submerged in the water, so if you have an open tank or your fish are jumpers it can’t really be used.

Suction cup submersible thermometer

These work in a similar way to the standing models, however they attach to the inside of the tank. It’s a good idea to place it near a filter or heaters where there is stronger flow of water going through because this will affect its accuracy .

This type gets ruined if the seal is broken when cleaning the tank. This problem often arises when the suction cup fails, allowing water to get in and ruin it.

Thermometer sticker strips (and why to stay away!)

These are cheap and not very accurate. They only last a week or so before they start to corrode and lose their stickiness, making them really hard to read because all you can see is the white backing!

Stick-on Thermometers are also known as Sticker Thermometers or Stickers. Sticker thermometer is a strip of chemical on which temperature is printed, so when this strip gets heated it starts to peel off

The problem with these is that they are hard to read because the backing paper tends to come up too, and they don’t last long. Even the best brands of these will only last a month or so.

It is easy to use, you just need to peel a sticker and attach it to the wall of the aquarium. Once it is attached it will detect the temperature of your fish tank.

This is not very reliable and should not be used if you want accurate readings.

Digital vs Analog – which thermometer is better for your aquarium?

Both of these are suitable as accurate types of aquarium thermometers, however they work in very different ways. Digital models use a battery-powered infrared sensor while Analog ones use a mercury bulb that sends an electrical current through it to get an accurate temperature reading.

Digital Aquarium thermometers use an infrared sensor to detect the temperature of your fish tank.

This is one of the most accurate types of aquarium thermometer since it measures the actual water temperature instead of air, however often these are made with plastic so be careful not to break them by applying too much force. These can come in a few different shapes and sizes, including some that are designed for submersible use.

Analog thermometer is the most commonly used aquarium thermometer because of its accuracy level.

These are more accurate than sticky strip type, and they can be used as a primary thermometer as they are easy to read. This detects water temperature by mercury bulb which sends an electrical current through it to get an accurate temperature reading. They are not very long lasting however, and they do need to be replaced occasionally.

What is the best and most accurate aquarium thermometer for your fish tank?

All of these thermometers are effective to an extent, however the most accurate and reliable is definitely the digital style one. This is because it directly measures the temperature of your fish tank without having to factor in air temperature. However, the submersible type models are best used to limit the chances of breakages when placed external to the tank. 

Where to Place a Thermometer in a Fish Tank?

This is a question that gets asked a lot! There is no right or wrong answer here, you just need to find a position in your aquarium where the temperature will be most stable and consistent. This may mean putting it closer to the heater, filter or at the bottom of the tank.

Try different places to see what works best for you.

It is important to place the aquarium thermometer at an appropriate place so you can monitor the temperature in your fish tank. If it is too low then you have to increase the temperature and if it is too high you’ll have to decrease the temperature.

How to clean aquarium thermometers?

Aquarium thermometers are generally pretty hardy, however if it’s a digital model then you have to ensure that water doesn’t penetrate the unit itself which could short out the sensor. It is recommended that you get a new one every few months just to be safe as they will get dirty over time.

What is the recommended water temperature in aquariums?

Well, it depends on the type of fish that you have. Tropical fish need a temperature of around 78F at a minimum

Generally the large size fish tanks need higher temperature (80-88°F (27-31°C)) and small size fish tank can use slightly lower range of water temperatures.

The last category of fish, Temperate fish is a new type of fish. These can be found in waters with differing temperatures and they generally require a greater range of temperatures.

It is important that you chose a combination of fish with the same temperature requirement. It is recommended that you keep big fish with big, bold and active nature in a tropical fish tank and small or less active fish in temperate aquariums.

As long as your aquarium is properly insulated and features a heater, providing stable temperatures will be easy. You want to make sure that both heaters are set on timers so they turn on only when needed. This will keep an ongoing, regular balance in your tank.

You need to be aware that even if your fish is surviving in the fish tank, it doesn’t always equate to it thriving. Fish need stable temperature to be comfortable and for this reason it is important that you monitor your tank regularly. This includes getting an appropriate aquarium thermometer to help you do so.

What to do if thermometer measurement is too low?

If the temperature is too low, you should increase it by using an aquarium heater. You should make sure that the heater you are using is sized according to your tank’s dimensions. If you buy an aquarium heater which is bigger than what is required, its effectiveness will be compromised and it might even cause problems such as overheating.

If the temperature of your fish tank exceeds beyond optimum level then you can decrease it by installing a cooling system.

What to do if the reading is too high?

This may be due to a number of reasons. It can be due to your heater not working properly or because you have set the temperature higher than the requirement. In this case you need to decrease the temperature.

If your aquarium is new then the temperature reading may be higher because of the heater startup period. If you are using an aquarium heater on a new fish tank, try setting it at its lower limit for a few days to ensure that everything settles down. Once the new fish tank has settled down it will have stabilised water temperature so there will be no large fluctuations.

Every aquarium owner should know that an aquarium thermometer is one of the most important tools for fish keeping, because it helps you adjust your tank’s water temperature to keep it within a healthy range. If you notice your fish tank’s reading is lower than the required safe zone, then you have to increase its temperature. Likewise, if the reading is higher, you then need to decrease it.

You will also have to keep in mind that fish scales can be used as a rough guide to the water temperature. If your fish feels warm and active, it’s safe to assume that your freshwater aquarium is within acceptable temperatures.

How do you maintain the ideal temperature in your aquarium?

There are many ways to monitor and control the temperature in your aquarium. If you do not have a good type of thermometer to keep track of the temperature according to your requirement, it becomes difficult for you to maintain a proper balance.

Nowadays there are several types of aquarium thermometers available from which people can choose. Some thermometers are very useful in maintaining the aquatic environment, whereas some can expose dangerous elements that can cause damage to your fish.


Choosing the right thermometer for your aquarium can be a tricky process. You’ll want to make sure you have the best type of thermometer that is suited for your needs, and one that will help maintain an appropriate temperature in your tank without causing any damage to fish or other marine life. 

In this article we outlined some different types of aquarium thermometers so you can decide which would work most appropriately with what you need from a water monitoring tool. We hope this information has been helpful!

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