1. Zacro LCD Digital Aquarium Thermometer
Key Features
Ideal for all water types
Easy suction cup fitting
Clear LCD display
– 50°C to + 70 °C temperature range
With many aquarists considering digital thermometers, the best for your fish, this high-quality thermometer with a probe more than fits the bill. Zacro’s LCD digital aquarium thermometer is compact and easy to use and offers an excellent temperature range (- 50°C to + 70 °C) so works with most tropical and cold water aquarium fish.
Despite the compact size of the display, we like how readable the LCD screen is and the operation is uncomplicated. Offering both Celsius and Fahrenheit, Zacro claim that the temperature accuracy is within one degree. The probe is small but easy to use in the water and the whole unit is battery operated, and pretty economical on its juice. For a starter aquarist or the more experienced, this is an excellent all-round LCD aquarium thermometer that for price, build quality and ease of use, tops our best aquarium thermometers list.
2. Marina Floating Thermometer
Key Features
Floating thermometer
Ideal for tropical fish
Safety zone indicator
Suction cup for security
Designed to float just under the water in a vertical position, not only is this Marina thermometer great value, but it is super easy to use. More suited to tropical fish, the whole thermometer can also be secured to the tank glass with a suction cup for extra stability and offers both Celsius and Fahrenheit readings. What is neat about this affordable thermometer is that the temperature measure also includes a safety zone temperature for identifying any water temp issues for your fish at a glance. The thermometer is a compact size so more suited for smaller tanks, but this means the printed temperatures are a little difficult to read. But for the price, this is a good everyday aquarium thermometer for tropical fish.
3. LCR Hallcrest Liquid Crystal Vertical Aquarium Thermometer
Key Features
Sticks on outside of tank
Easy to read display
Can be moved around
Reads in Fahrenheit
For freshwater tanks, stick on thermometers can be an easy-to-use option, as long as the room temperature does not have too many fluctuations or if the seasonal variations are extreme. And as a way to get started for temperate water fish they can work pretty well. These stick-on water temp thermometers from LCR Hallcrest use liquid crystal to measure the water temperature via the outside of the tank. It is unobtrusive, easy to fit and pretty secure although it won’t have an endless shelf-life. However, it is surprisingly accurate, as long as it is used in the correct way and you don’t keep your tank near to any external heat sources such as radiators or direct sunlight.
4. Keynice Digital Thermometer
Key Features
Blue backlight digital display
-58F to 230F (-50°C to 110°C) range
Fahrenheit to Celsius selector switch
±1℃ temperature rating
With its vibrantly clear display screen and USB power source, this digital thermometer from Keynice is a nice bit of kit for any aquarist. As a multi-purpose digital thermometer – it can be used for in-water as well as a host of other dry uses – it is also versatile which makes it a good investment. The probe is waterproof and while some reviewers say the cable is a little on the short side, it should work with most fish tank set ups. And as it is rechargeable, there’s no need for batteries. The blue backlight of the display makes it really easy to read, even in the dark and you get both a numerical reading as well as a thermometer graphic. You can choose between Celsius and Fahrenheit and the temperature range of -58F to 230F (-50°C to 110°C) makes it suitable for both tropical and cold water fish. Add in a decent accuracy of ±1℃ and you get a smartly accurate aquarium thermometer for your money.
5. SUKRAGRAHA Traditional Stick-on Aquarium Thermometers
Key Features
Traditional stick-on style
10 thermometers per pack
64-93°F (18-34 °C) temp range
Easy to fix and remove
Straightforward and easy to use, there is nothing particularly fancy about these traditional stick-on aquarium thermometers and that is part of their appeal. They are clear and simple to read, the adhesive is secure, and each strip is a decent size. You get a pack of 10 and this is a good idea as each thermometer is not reusable once you peel them off your tank. However, the temperature range is a little limited – 64-93°F (18-34 °C) – compared to other thermometers in our review so won’t be as accurate should you suspect your water temperature has fallen too low or risen too high. However, as a back-up, or for use if you are transporting your fish, we think these stick-on thermometers work pretty well and won’t break the bank.
6. JW Pet Company Smarttemp Thermometer Aquarium Accessory
Key Features
Secures to tank via a magnet
Made from durable plastic
Green zone for optimum temperature
(+/-) 1.5-degree accuracy
Suction cup free, this standing in-water thermometer uses magnets to fix to the inside of your tank, so leaves no marks or residue when it is removed. This makes it easy to use and move around. It isn’t the biggest of aquarium thermometers you can buy – it’s about six inches long – but the temperature measures in both Celsius and Fahrenheit are clean to read. Plus, you get a green zone to let you know at a glance if your water is in the optimum temperature range. The full temperature range should be enough for most fish tanks set ups and as a simply designed thermometer, the accuracy rating of (+/-) 1.5-degree usually balances out.
7. Prairie Essentials Instant Easy Read Stick On Thermometer
Key Features
Two thermometer pack
Removable self-adhesive
58°- 88° F (14°-31° C temp range
Easy to read red display
With no need to plug in or change batteries, the appeal of stick-on liquid crystal thermometers is the ease and convenience of use. However, as they are on the outside of the tank, they are not generally as accurate as in-water thermometers or probes. As a stick-on thermometer, Prairie Essential’s Liquid Crystal Thermometer is a popular choice and each thermometer in this two-pack is moveable and reusable. The temperature readings are in clear red against black and you get both Fahrenheit and Celsius to choose from. As with most stick-on thermometers, the temperature range is not as wide as other types of thermometers and with Prairie Essentials, you get enough for most home tanks – 58°- 88° F (14°-31° C). The reading is quick too but as these types of fish tank thermometers can be affected by ambient temperature, they may not be quite on point as a digital aquarium thermometer.
8. Qooltek Digital LCD Thermometer
Key Features
Extra-long probe cable
Easy to mount on your tank
Clear digital display
-14°F ~ +122°F range
Our premium pick is this solid-looking digital aquarium thermometer with probe so you can get an accurate reading of your tank water at any time of day or night. It may be at the top end of our review budget, but its accuracy is good and the whole thermometer is hardwearing and long-lasting. The probe has a decent cable length – 3.3 feet – for convenient set up and the console has a mounting hole so you can choose how to fix it to your aquarium. The temperature range of -14°F ~ +122°F covers all your fishkeeping bases and means the thermometer can also be used for other things, including refrigerators or reptile tanks too. Battery operated, you don’t need to worry about recharging or a separate power supply either as it has a two-year battery life.
9. capetsma Aquarium Thermometer
Key Features
Stick-on temperature sensor
Battery operated
Touch screen display
High and low temp warnings
Taking the digital display tech of a digital thermometer and the convenience of a stick-on design, Capetsma has produced a neat external thermometer for most domestic aquariums. This clever sensor sticks on the side of your tank – ideally placed below the water line and away from any aquarium heaters – and displays the temperature clearly. It is also touch sensitive so you can set your own high and low temperature warnings, depending on your tank inhabitants as well as switch from Celsius to Fahrenheit as needed. The overall design is attractive and while it is sizeable, shouldn’t overwhelm or clutter up your tank glass. It is also battery operated, with an extra battery supplied as part of the pack. Suited to both fresh and saltwater aquariums, the Capetsma can also be used for terrariums as well as DIY homebrew beer.
High-Accuracy, Low-Cost Aquarium Thermometers Buying Guide
What is an Aquarium Thermometer?
Simply put, an aquarium thermometer is a tool you can use to accurately measure and monitor the water temperature inside your fish tank. It works in the same way as an ordinary thermometer but a fish tank thermometer has been designed for in-water use so you can ensure the water is perfect for your fish. Aquarium thermometers come in a choice of designs (more on this later) and are easy to use and install.
Benefits Of Aquarium Thermometers
As you need to create optimum conditions for your fish inside their tank, an aquarium thermometer is an essential piece of fish care kit. There are numerous benefits to using a fish tank thermometer:
- They are easy to use and install
- You get accurate readings at any time so you can monitor any temperature fluctuations which may be detrimental to your fish
- They enable you to ensure your tank heater is working at its best
- Some thermometers can be set to track the ideal temperature and alert you to any issues
- An aquarium thermometer ensures your fish are happy, healthy and thriving in their temperature-controlled water environment.
Features to Consider When Choosing an Aquarium Thermometer
Getting the right aquarium thermometer for your fish and tank set up is essential. Here are key things you need to consider:
Thermometer type: Choose the type of aquarium thermometer that suits your budget as well as your aquarium and type of fish you intend to keep. There are three main types – digital, standing or floating and stick on. Digital aquarium thermometers are the most accurate and a good choice if you have more temperamental and water temp sensitive tropical fish while the classic standing mercury or crystal thermometer is easy to use and when fully submerged, is suitable for a range of tanks and fish.
Durability: Not only does your aquarium thermometer needs to be built enough but it needs to be durable enough to be safe for use with live fish. Digital thermometers should include a probe so it can be safely used in the water and if you are opting for a classic standing style, it needs to be made from crack resistant materials, so the mercury contents don’t enter the water.
Accuracy: As the temperature of the water can have a significant – and potentially fatal – impact on your fish, the accuracy of your aquarium thermometer is a crucial consideration. The more accurate the fish tank thermometer, the better so always look for a thermometer that is able to give a reading within +/- 1 degree Celsius. Digital aquarium thermometers with an LCD display tend to be the most accurate, and so offer the best aquarium thermometers but they can also be the most expensive.
Temperature range: As well as accuracy, check that the temperature range of your fish tank thermometer meets the needs of your aquarium inhabitants. If you keep tropical fish, then the thermometer will need a larger range - in both Celsius and Fahrenheit - than a thermometer used for cold water fish.
Readability: A thermometer you can’t easily read is not going to be a helpful piece of kit so always opt for a thermometer with a clear display, especially if it is submerged under the water. Thermometers with LCD displays are the easiest to read, as are large display standing styles.
Easy to install and use: Try to avoid an over-complicated fish tank thermometer as it will take more time to use and with more components, is more likely at some point to go wrong. Even with a digital thermometer with a probe, you want to be able to quickly set it up and go.
Why You Should Avoid Thermometer Sticker Strips
Many aquarists prefer not to use the stick-on option when it comes to fish tank thermometers, despite how easy they are to fit and use. And the reason is that as these sticker-like thermometers have to be affixed onto the outside of the tank. And this can cause issues with the accuracy of the temperature readings. This is due to the external influences such as direct sunlight, central heating and general fluctuations in air temperature which can cause the stick-on thermometer to give an inaccurate reading of the water temperature inside the tank. And they are not that long-lasting either and tend to eventually peel off. So, for the health and water temperature safety of your fish, opt for another style of aquarium thermometer instead.
Different Types of Fish Tank Thermometers
There are three different types of aquarium thermometer commonly used inside fish tanks, with some more effective than others. The three types are:
Digital: Designed with a probe that sits underwater in your aquarium, and a display that fits above the water on the outside of the tank, digital aquarium thermometers are the most accurate as they are not affected by ambient temperature. However, they can be the most expensive to buy. The digital display is easy to read and can be set to either Celsius or Fahrenheit; most are powered by batteries and you can also choose between wired and wireless operation. Added features include an alarm if the water drops below the desired temperature and on the whole, digital thermometers are great value as they are durable and long-lasting.
Standing or floating: This type of thermometer needs to be totally submerged in the tank for it to work. As a result of this submersion, there is no digital display and the whole thermometer looks similar to ones you may find in your medicine box. Typically cheaper than digital thermometers, a standing or floating device is typically made from glass or plastic and you need to read the temperature display in-water. For security, most come with suction cups so you can stick them on the inside of the tank glass, while you can also get free-floating designs. Easy to use, there are downsides too – the glass can be fragile, they are not always as accurate as digital, but they do the job.
Stick-on: With a basic LCD display, stick-on thermometers need to be located on the outside of the tank and so are not as accurate as their readings don't come directly from the water temperature and can be affected by the room air temperature too. Their accuracy can also be hampered by direct sunlight, air vents and any heaters in the room. A basic way to measure water temperature, stick-on thermometers are not recommended, especially if you are keeping warm water fish.
The Best Temperatures For Various Kinds of Tank Inhabitants
As a basic guide to the temperatures you should be maintaining, depending on your aquarium and your chosen fish tank inhabitants, we've together the below:
Fish type Ideal temperature range
Saltwater tropical 75-85°F (24-30°C)
Freshwater tropical 65-85°F (18-30°C)
Reef tank 70-82°F (21-27°C)
Temperate water 59-82°F (15-28°C)
Cold water 60°-75°F (15-24°C)
Our Top Pick
For price, ease of use and quality, the compact Zacro LCD Digital Aquarium Thermometer comes out best in our aquarium thermometers review. Despite its small size, this is a big performer, with an excellent temperature range that covers both cold and warm water fish. With a suction cup fitting, it sits securely and the display is easy to read. We think this is a thermometer that both you and your fish will really warm to!
