Cookies seem to be disabled in your browser, therefore this website will NOT work properly! Please, consider enabling Cookies in order to maximise your user experience while browsing.
Recent discussions at Aqua-Fish+
  1. PondSealer at Maintainging a garden fish pond tasks on
  2. TheFishWorks at A guide on growing aquarium plants with FAQ, forum and species on …display more of the recent discussions
  3. Salviashaman at A guide on caring for Congo tetra (Phenacogrammus interruptus) on
  4. Salviashaman at A guide on setting a South American blackwater stream biotope aquarium on
  5. Figureguy at Chemistry of Aquarium Water with FAQ on
  6. Jackson20 at A guide on feeding aquarium fish frozen foods on
  7. Senator Wisdom at Bloodfin tetra (Aphyocharax alburnus) on
  8. CayceR at A page and forum devoted to keeping Blood parrot cichlids on
  9. Ness at A guide on raising African Dwarf Frogs with pictures and forum on
  10. Terry Mitchell at A guide on breeding, feeding and caring for L333 Pleco on

Aquarium Thermometers - Instructions, Suppliers, FAQ and Forum

Resized image of stick aquarium thermometer - shows Celsius and Fahrenheit degrees

Brief Description

If you came here searching for online suppliers of aquarium thermometers, simply follow this link! The article below is dedicated to using fish tank thermometers and answers questions that have been asked by our visitors. In a case you are unable to find answer on your question below, use a form at the bottom of this page and we'll answer!


When it comes to keeping your tropical freshwater aquarium maintained and a safe environment for all that lives within, no piece of equipment could be more essential than the aquarium thermometer. These devices vary in the materials from which they are made, and they span a price range from cheap to expensive. The type or brand of thermometer you purchase is not as important as the fact that you do purchase one for your aquarium. The aquarium thermometer size is not significant, big thermometers should give the same readings as small thermometers!

The fish and other creatures which dwell in a tropical aquariums can be very sensitive when it comes to the temperature of the water around them. Temperature changes that are too dramatic will result in death to many of your expensive tropical fish and little creatures which scuttle back and forth across the bottom of the tank floor.

Having your investments die, (and let’s face it, tropical fish aren’t cheap) from temperature changes is completely avoidable by simply purchasing and installing an aquarium thermometer. Since these devices come in all shapes, sizes and price ranges, there most certainly is a thermometer which is right for you.

The difference between heater and thermometer

Remember that the thermometer and aquarium heater are not the same equipment, the thermometer tells you the temperature that the heater is heating the water to. Always purchase the most accurate thermometer that you can afford, these are always the most accurate, digital thermometers can be accurate to a tenth of a degree.

The thermometers should be checked on a daily basis to make sure that the heater is working properly or if it needs adjusting to compensate for room temperatures raising or lowering the water temperature.

Reading a thermometer

All thermometers are easy to read, the glass models have a scale display and the higher end of the market thermometers will have a digital screen for you to look at. Always stand directly in front of the glass thermometers to get an accurate reading, these will also have a green mark on the scale, this is where the temperature should be inside the mark if your heater is working properly. Outside of the green mark means that the temperature is too high or too low.


Installation of aquarium thermometers is very simple, even if you decide to go with the high end models. Let’s look at a few which are available right now.

For those of you who have spent most of your cash on tropical fish and other denizens of the deep to inhabit your aquarium, there is the Penn Plax Floating Thermometer which will set you back a miniscule $1.60.

This frugal device is a small pen shaped floating thermometer that you can stick to the inside of the tank with the included suction cup, or you can let it float merrily along on top of the water. This aquarium thermometer reads from 20 to 100°F (~ -6 - 38°C) range. Devices of this type are constructed of plastic, and in some cases they will have a glass casing, and can be hard to read if free floating. If the glass or plastic were to break then all fragments must be removed from the aquarium or the fish could injure themselves on the shards. This type of thermometer must be placed in the water to get your temperature reading but they tend to be less accurate than the more expensive styles of thermometer. The main advantage of these is the cheap outlay and installing them literally takes 2 seconds, they need to be attached to the front or the sides of the tank so that you can see the reading easily.

The strip thermometer

If you’ve managed to save a bit more of your pocket change, you opt to go a little higher up the price ladder by purchasing the Marina Minerva. This thermometer will set you back a mere $1.99. This style of thermometer is also known as a strip thermometer and must be installed on the exterior of the glass, the same as with the floating thermometers, make sure that it is clearly visible for you to take the readings. This aquarium thermometer will allow you to see the water temperature in either the Fahrenheit or Celsius temperature scale. It mounts easily on the exterior of the tank by means of a sticky backing paper and reads in the range of 66 - 86°F and 19 - 30°C.

Digital thermometers

Digital thermometers are by far the more popular types of aquarium thermometers. For a small sum of around $7.50 you can purchase one of many brands of basic digital thermometers. These are the type which attach to the exterior of the aquarium and are easy to use and read. This style of thermometer is by far the most accurate and very easy to read from the display. These thermometers are battery powered and use a probe which is inserted into the tank, which read in the range of -10 to 140 degrees Fahrenheit and -23 to 60 degrees Celsius.

Digital aquarium thermometers can vary in price, as do the features available. Some simply tell the current water temperature, while others tell the time and temperature. Even more, there are models which have a built in memory that can tell you the all time water temperature high and low since it was installed. Still others will have audible alarms to alert the owner that the water temperature has dropped or risen beyond a preset level.

Installing the probes into the tank is also very simple as they are mounted by a suction cup and a wire leads back to the main display, always make sure that the wire is not left dangling loose in the water as the fish can get tangled in this and it is more liable to get damaged itself.

Pros and cons of a digital one

The main advantage of using a digital thermometer is the high degree of accuracy and the easy display, they are accurate to one tenth of a degree in most cases, the only real disadvantage of using them is the initial outlay but as there are more available the cost is starting to drop.

On the high end scale of aquarium thermometers, you can find models which do all the above, and are wireless remote as well. This allows the thermometer to be installed on the tank, and have the current temperature to be displayed on a display monitor anywhere in the home. It’s also possible to have a display located in multiple areas, (up to four) so you can be almost anywhere in the home and see the aquarium water temperature.

Whether you choose to go with a pen thermometer or a full duplex model is completely up to you. Either way, if you are comfortable with the performance of the model and make you’ve chosen, then its money well spent, no matter how much or how little it cost you. What a tragedy it would truly be to spend the time and money to have a tropical freshwater aquarium filled with beautiful tropical fish and lose them because you failed to spend a couple of extra dollars to purchase an aquarium thermometer.

As stated earlier, it really doesn’t matter what brand it is, or even how much you pay for your aquarium thermometer, the important thing is that you actually have one installed and that you read it regularly, this will need doing at least once a day. Keeping your tropical aquarium within optimal temperature range will help maintain the well being of the fish and other creatures that you’ve welcomed into your home. All aquarium thermometers are waterproof so there is no reason why these same models of thermometer cannot be used for another purpose such as being placed into humid reptile or spider tanks. You do not need to hunt for separate models of thermometer; they will cover both sorts of pets!

Aquarium thermometer

Questions and answers

On March 23th 2011 we added the following answers here due to merging with related articles. You're welcome to post own questions at the bottom of this page as long as they're unique and not yet answered on this page!

  • Where should I put my aquarium thermometer?

    Answer: It depends on if its for usage in aquarium or for outside of your aquarium. Submersible thermometers should be placed somewhere in the corner of your tank. Stick thermometers should be placed on the front glass of your aquarium and they should be always visible. Not too high, not too low.

  • What type of aquarium thermometer should I use?

    Answer: There are black temperature strips that have an adhesive backing for sticking to the outside of the aquarium glass. The water temperature is revealed as the thermometer colours change depending on how warm or cold the water is. This is not always the most accurate reading because it usually reads a couple of degrees higher or lower than the water actually is. These thermometers usually have a small range of temperature to read, somewhere between 64 to 84°F (~ 18 - 297deg;C). Digital thermometers which are also fixed to the exterior glass can provide a more accurate reading. Not only are they able to tell you the exact temperature of the aquarium but they also read a wider range of temperatures, for example -10 to 140°F (~ -12 - 60°C). There are also other features that make digital thermometers more useful, such as high and low readings, alerts when temperatures rise or fall outside of a desired range, and LED display lighting.

Online suppliers

If any of the links shown below doesn't work, inform us via form that is at the bottom of this page, please! If you know some good pet store that you'd like to recommend, use that form too!

Please, verify whether your login and password are valid. If you don't have an account here, register one free of charge, please. Click here to close this box.

You have been logged out successfully! This box will close automatically!

Something went wrong during processing your message, please try again!

Your message has been sent, thanks a lot!

Page has been saved, refresh it now, please!

The page has been created, you will now be redirected!

URL already exists!

Path to the photo is not unique!

Really delete this page from the database?

The page has been removed successfully, you will be redirected now!

The page couldn't be deleted!!

Unfortunately this page doesn't allow discussion. Please, find any other page that fits your area of interest as over 99% of our pages allow discussion. The reason why no discussion is allowed here is this page is too general. Thanks a lot for understanding! Click here to search, please!

Really delete this comment from the site?

Really delete this image from the site?

Really delete this image from the site?

Selected comment has been removed successfully!

Selected image has been removed successfully!

Either login or email address is required

Account has been recovered, please check your email for further instructions