Imagine waking up one morning only to discover that all your fish are floating upside down at the top of your aquarium.
You feel the water only to discover that it is boiling. You have cooked your fish!
This scenario is more common than you might think. All it takes is for your heater to remain on longer than it should, and you risk overheating your fish.
That’s where an aquarium heater controller comes in.
This important device may just save your fish’s life. And today, I am going to teach you all about it.
hygger Saltwater Tank Aquarium Heater with Digital Thermostat
What is an aquarium heater controller, and how does it work?
As the name suggests, an aquarium heater controller allows you to precisely regulate the temperature of your fish tank – much more accurately than just using an aquarium heater alone.
Think of a temperature controller as an external thermostat specifically for your fish tank.
There are two types of aquarium temperature controllers:
- Pre-wired temperature controller – Comes as a complete unit. Simply plug your heater in, and you are good to go. No more effort required!
- DIY temperature controller – As the name suggests, you buy the parts separately and create your own temperature controller. Electrical knowledge is recommended if attempting to create your own.
While the exact style of an aquarium temperature controller will vary according to the brand, it will typically consist of three distinct parts…
The controller consists of a digital LCD screen and buttons that you can use to set the desired temperature.
This is the brains of the equipment. The controller monitors the water in your aquarium to ensure that it is always at the correct temperature.
Pretty self-explanatory. This is where the plug from your aquarium heater goes.
Some temperature controllers come with two independent outlets – one for a heater and another for a chiller.
These are called dual temperature controllers, and they allow the controller to heat the water when it’s too cool and chill the water when it’s too hot.
3. Temperature sensor probe
The waterproof probe sits inside your aquarium and measures the temperature of the water.
Be mindful that if you have a saltwater tank, you will want a probe that is resistant to corrosion.
How does the temperature controller work?
Without boring you with the complicated technical details, how a temperature controller works is actually very simple.
Step 1. Set your temperature
Using the controller, you set the desired temperature. In this case, I am going to set it to 79 degrees Fahrenheit (26 degrees Celsius) – because that’s what my angelfish prefer.
Step 2: The controller reads the temperature
Using the sensor probe inside your tank, the temperature controller will read the temperature and compare it to the temperature that you set.
Step 3: The controller takes action
If the temperature is colder than what you have set, the controller sends power to the sockets, which turns on your heater.
Once the temperature is reached, it shuts the heater off until the temperature drops again.
That’s all there is to it!
Why you need an aquarium heater controller?
It’s very likely that the aquarium heater you use already has a thermostat inside it. And when it reaches a certain temperature, it turns itself off.
So then, why do you need a temperature controller for your aquarium?
Well, it turns out that there are two good reasons…
1. Heater malfunction
Well, the reality is that heaters fail.
Your heater could fail due to poor manufacturing, incorrect installation, user error, electrical fault or any other number of reasons.
Yes, the chances of your aquarium heater failing are low…
But if it does fail, your tank will overheat, and you can kiss your tropical fish, plants and corals goodbye.
It’s an expensive accident that can be prevented with an aquarium temperature controller.
Once the water reaches the temperature you set, the controller will kill the power to your heater, turning it off.
If your aquarium heater also has a thermostat, then the temperature controller is an extra layer of safety.
2. The thermostat and sensor are better quality
I have to hand it to modern aquarium heaters – they manage to squeeze a thermostat, temperature sensor and heater element into a tiny product that barely takes up any room in your tank.
But the downside is that these components are not as accurate. If you need a narrow temperature range for breeding or have very sensitive fish, then you need a more accurate way to determine the temperature of the water.
That’s where a controller comes in – offering a precise measurement of the water temperature.
How do you choose the right heater controller for your aquarium?
To narrow down the ideal temperature controller for your aquarium, you need to answer the following questions:
1. What heater do you need to control?
As you are probably aware, the power of your aquarium heater is measured in watts (W).
You can find the wattage rating of your heater printed on the box or in the manual of your aquarium heater.
This rating needs to fall in line with what the temperature controller outputs, otherwise the controller may fail.
Let’s say the temperature controller has an output of 1000W. This means that it can control one 1000W heater, two 500W heaters or any combination of heaters adding up to 1000W.
But if you need the temperature controller to run an 1100W heater, you risk the temperature controller failing.
So, you want to make sure that your heater wattage is equal to or less than the output wattage of the temperature controller.
Note: Most temperature controllers are more than capable of handling heaters for smaller tanks – this is mostly an issue for larger tanks that need bigger heaters.
2. Is your tank freshwater or saltwater?
Good news for those of you with freshwater tanks – you can use any waterproof probe to measure the temperature.
But those of you with saltwater tanks may experience some grief. Yep, that salt water quickly corrodes most metals, including your temperature probe.
Fortunately, many temperature controllers allow you to swap out the probes. Simply buy a temperature probe that is saltwater friendly (titanium is a good choice), and you are set.
If swapping out the sensor isn’t an option, try a DIY solution. This was recommended to me by a couple of reef tank enthusiasts.
You can either seal the probe in an epoxy or cover it with heat shrink. I have not tried either of these solutions and would love to hear from any of you who have had success with these methods.
3. Do you also need to cool your tank if it gets too hot?
A temperature controller that performs just one function, such as heating, is called a single stage temperature controller.
But you can also buy temperature controllers that allow you to both heat and cool your tank.
These temperature controllers are referred to as dual stage temperature controllers.
How a dual stage temperature controller works is actually really simple.
Whatever you plug into the cooling socket will activate if the temperature in your aquarium is above the preset temp.
And, anything that you plug into the heating socket will activate if the temperature falls below your preset temp.
This allows you to keep your tank in an extremely narrow temperature range regardless of the temperature outside the tank.
4. What are your DIY skills?
Last but not least, your electrical skills and knowledge play a major part in what temperature controller you use.
Just want a simple option that you plug in and forget about?
Then, you want a pre-wired temperature controller. As the name suggests, this controller comes as a complete unit. Simply plug it in, and you are ready!
But if you want specific features or need to use a heater that exceeds the capabilities of pre-wired models, then you will need to wire it yourself.
Or maybe you want to add features that are not available on pre-wired temperature controls…
Want to create a temperature controller that heats at different temperatures during the day and night? You can do that.
Want an alarm to sound at a specific temperature? You can do that too.
You are only limited by the components that you add to the circuit.
While this DIY approach allows you to create a custom temperature controller to suit your exact needs, it does have an element of danger.
If wired incorrectly, you risk serious harm to both yourself and your fish. And while it may look safe, you could have accidentally created a ticking time bomb.
If you need a custom temperature controller, I recommend buying the components yourself and then paying a qualified electrician to wire it.
Remember, it’s okay to pay someone for the skills you lack!
What is the best aquarium heater controller?
Now that you are familiar with the basics, it’s time to take a look at some of the most popular and reliable temperature controllers on the market.
Best all-round aquarium heater controller
- Model number: ITC-306T
- Power supply: AC 110V ~240V
- Temperature range: -58°F ~210°F (-50 ~99°C)
- Max load: 110V – 1100W (240V – 2200W)
The Inkbird pre-wired temperature controller is perfect for beginners and those who like to keep things simple.
The Inkbird ITC-306T offers complete temperature control at an affordable price.
But best of all… It just works.
Setting up the temperature controller takes just minutes.
Plug in the temperature controller, plug in your heaters, place the sensor in your tank and set the temperature limit.
It really is that simple!
What I like best is the twin digital LCD screens. One shows the current temperature of your tank while the other shows the maximum temperature you want it to reach.
Inkbird also has a couple of handy safety features included – an alarm sounds if the sensor probe has a fault or if the tank water exceeds the temperature you set.
But what if you need both heating and cooling?
Well, Inkbird has a product for that too.
Introducing the Inkbird ITC-308, a dual stage aquarium temperature controller…
- Model number: ITC-308T
- Power supply: AC 110V ~240V
- Temperature range: -58°F ~210°F (-50 ~99°C)
- Max load: 110V – 1100W (240V – 2200W)
The ITC-308T works the same as the ITC-306T with one small exception – it allows you to cool your tank when the water is too hot and heat your tank when the water is too cold.
It does this by using dedicated sockets – one for your chiller or fan and the other for your heater. Each outlet is activated independently, depending on the temperature of the water.
Inkbird also makes a WiFi Smart Temperature Controller that allows you to view the temperature and receive alerts on your smartphone.
Being able to monitor the temperature of your tank sounds pretty handy, right?
Unfortunately, it works better in theory than in practice…
At the time of writing, I could not get the app to work with Apple’s newest iOS release. And as for Android, user reviews report that it’s plagued with problems.
I have yet to come across an affordable (under $100), reliable and easy-to-use prewired WiFi temperature controller. I have tried Inkbird and Willhi’s models but cannot recommend them based on my experience.
If you know a great WiFi temperature controller that fits the above criteria, please let me know in the comments!
Best DIY aquarium heater controller
- Model number: ETC-111000-000
- Power supply: AC 110V ~240V
- Temperature range: -30°F ~220°F (-34 ~104°C)
- Max load: 120V – 1800W (240V – 1800W)
For those of you who are just looking for quality components to make your own temperature controller, look no further.
The Ranco, by Robert Shaw, temperature controller is used in a wide variety of industrial applications, from beer brewing to HVAC systems. And, it’s just as suitable for your aquarium.
The unit is well documented with easy-to-understand wiring guides, specifications and instructions. You can grab a PDF copy of the manual here.
Please note that the model above is a single stage temperature controller. While you can use it to heat or cool your aquarium, it can only do one at a time and will need to be re-wired if you want to swap it over.
The dual stage model allows you to wire both a chiller and heater at once. You can find it here, and the instruction manual here.
Johnson Controls also makes fantastic temperature controls, manufactured right here in the USA. These industrial-grade temperature controllers are praised by technicians for their reliability and build quality. Check it out here, and view the instruction manual here.
While both are great temperature controllers, I recommend Robert Shaw’s Ranco because it is more widely available, often at a cheaper price.
One more option…
Are you looking for an advanced water heater and digital thermostat for your aquarium? Then, this product from hygger is one of the best options in the market right now.
The hygger Saltwater Tank Aquarium Heater with Digital Thermostat comes with a fully submersible design. Thanks to the suction cups, installing the product on the water tank is an easy task. In addition, by keeping it near the water source, you can enable aquarium-wide heating quickly.
Because the device is expected to be fully submersible, the build quality is up to the mark. In particular, the titanium heater can stand against corrosion and shattering. The company has not used glass in these parts, making sure that accidents do not occur.
The hygger Saltwater Tank Aquarium Heater with Digital Thermostat also uses one of the best thermostats you can find today. You can see the temperature in different units as per your needs. There is also the proper circuitry for an automated shut-down system, which comes in handy.
Last but not least, this water heater controller is suitable for large tanks. You would not have any trouble using it with tanks as large as 45 gallons. You can also choose one of the more powerful products if you have a larger aquarium.
- It comes with a premium design
- Additional heating performance
- Secure and automated circuitry
- Suitable for larger aquariums
- It can be expensive for some
- It has a relatively bulkier design
As you see, a temperature controller is an essential fail safe for your aquarium.
If you are still put off by the idea of purchasing yet another piece of equipment for your tank, consider this…
Imagine how costly it will be to replace everything if your heater fails.
What do you use as a temperature controller? Let me know in the comments below!
Ian Sterling, founder of Fishlab.com, began his aquarium journey over 30 years ago, driven by a deep fascination for fish and their diverse personalities. His website, Fishlab.com, is dedicated to making fishkeeping accessible and enjoyable, offering beginner-friendly guidance, expert insights, and a community for aquarists to connect and share experiences.