5 Best Heaters for Small Aquariums (1 to 10 Gallon Fish Tanks)


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Your small tank needs a heater, but there isn’t really room for it? What do you do? Do you get a bigger aquarium? Or do you invest in a small aquarium heater instead?

Luckily, there are heaters designed for small aquariums that will not take up too much space and ensure the right water temperature for your fish so that you don’t have to upgrade to a bigger aquarium unless you really need to.

If you’re looking for a convenient way to heat your tiny aquarium, read my tips below on the best small aquarium heater for fish tanks under 10 gallons.

Do You Need a Heater for Your Fish Tank?

If you have tropical fish that require warmer water that what your average room temperature, then a heater is indeed needed.

A heater is even more so of a requirement in a small aquarium, which is more exposed to temperature variations due to the small water volume.

These variations in temperature are stressful to your fish and can cause diseases and even death.

An aquarium heater will help keep the water temperature stable and your fish healthy.

How to Choose a Heater for Small Aquarium?

When choosing a small aquarium heater, there are a few things to consider, namely:

  • The size of your aquarium (water volume);
  • The temperature in your room;
  • The temperature that’s required in your aquarium.

The power of small aquarium heaters is measured in watts and the higher the wattage, the more powerful the heater. For example, a 50 W heater is enough for a 10-gallon aquarium.

Therefore, when looking for a heater for your small aquarium, check that it’s rated for the tank size you have.

Another thing to consider is temperature adjustability. If you get a preset heater, which has a preset temperature (it doesn’t allow you to adjust the temperature), make sure you also get a temperature controller.

Alternatively, you can get a heater with adjustable temperature or a built-in thermostat, which allows you to select the temperature within a predefined range.

These heaters have an automatic shut-off system that switches off the heater once the preset temperature is reached and starts again once the temperature drops.

Best Aquarium Heater for Small Fish Tanks

In this article on best small aquarium heaters, I’ve chosen to review best-in-line heaters for every price range, so you can see how a more expensive heater compares to an affordable one.

I’ve selected the aquarium heaters below for their efficiency, size, and their compatibility with small aquariums.

If you want the best small aquarium heater for your tiny tank, you can’t go wrong with the following products:

1. FREESEA Submersible Aquarium Heater

This submersible heater is a space-saver designed for warming the water in tiny aquariums. It features a LED temperature display and it’s available in different power sizes (50-300Watts).

The Freesea Aquarium heater must be submerged in water (heating rods must stay under water) and should not be left to run dry. When cleaning the tank or when changing the water, you should unplug the heater to prevent it from overheating.

You can set the desired temperature 59°F~94°F(15°C~34°C). The system’s automatic constant temperature function acts as a built-in thermostat turning off the heater when the desired temperature is reached and turns the heater back on if the temperature drops below the predefined value.

The LED display is illuminated for greater visibility, allowing you to monitor its operation more easily. The heater comes with a 12-month warranty.


  • Small size, rounded off shape for those who don’t like cigar-shaped heaters;
  • LED display for easy temperature monitoring;
  • Built-in thermostat;
  • 12-month warranty.


  • Design flaws (small fish can get stuck in the plastic covering the heater), not recommended for small fish;
  • No overheating protection when running dry.


2. Tetra HT Submersible Aquarium Heater

The Tetra HT submersible aquarium heater line offers heaters for rated for 2 to 55-gallon tanks. The heater features a built-in thermostat that keeps the temperature at a stable 78 F.

The heat indicator lights let you know when the heater is on (red light) and when the preset temperature has been reached (green light).

The heater is fully submersible, and you can install it either vertically or horizontally. Because of its small dimensions, you can hide it with decorations and plants.

The Tetra is equipped with a shut-off system that jumps into action if an electrical short is detected, cutting the power off.

Since this is a preset heater, I recommend using it with a temperature controller to make sure it switches off when it’s supposed to.

Because small aquariums have less water volume, they tend to lose heat much faster than larger aquariums. Therefore, I recommend using a hood or glass canopy with your tank to contain the heat inside and maximize heater efficiency.


  • Easy to install in whatever position you need it;
  • LED light system for heater operation monitoring;
  • Built-in thermostat.


  • Preset heater with no possibility to adjust the temperature, the heater is set to 78 F;
  • No overheat protection.


3. GOOBAT Mini Heater for Aquariums

The Goobat Mini aquarium heater is another preset heater that you should consider for your small aquarium. It has a preset temperature of 77 F (+/- 1) without needing manual temperature adjustment.

It’s available in two sizes, one for 1-5.5 gallon tanks, the other for 6-10 gallon aquariums. The heater is made of PPC plastic, and it’s easy to install in your aquarium with the help of the suction cups provided in the kit. The heater also features a red LED indicator that lets you know the heater is in function.

This submersible heater is designed for small betta aquariums, which require a heater because of the higher water temperature requirements of betta fish.

If you keep your betta in a small tank, keeping the water at the right temperature for them can be a challenge seeing how air temperature changes can easily affect the temperature in your aquarium.


  • Space-saving design;
  • Easy to install with suction cups;
  • Temperature variation is within 1 degree;
  • Different models available depending on the size of your aquarium.


  • Requires temperature controller for extra safety;
  • No possibility to adjust temperature.


4. Aqueon Flat Submersible Heater

Another small heater to consider for your tiny aquarium, the Aqueon Flat, is a submersible heater with a flat design that’s available in two sizes for aquariums up to 10 gallons.

The heater is fully submersible, shatterproof and it can be installed vertically or horizontally with the suction cups that are included in the heater kit. It’s ideal for glass or acrylic Desktop-style fish tanks.

If you’re keeping small tropical fish in an aquarium that’s under 10 gallons, this submersible heater can be the space-saving solution to heat your tank.

Like with many submersible aquarium heaters, this too should not be left to run dry. Always turn it off when cleaning the aquarium or performing water changes.

Now this may not be a fancy piece of equipment (no LED display or indicator), but it’s also extremely affordable.


  • Sleek flat design, it doesn’t take up much space;
  • Affordably priced;
  • Keeps water at steady temperature (78 F)


  • No possibility to adjust temperature;
  • Requires temperature controller.


5. Fluval Marina Submersible Heater

This last heater on my best small aquarium heater list is another submersible heater, this time one that allows you to set the temperature with the help of a temperature dial located on the top of the heater.

The heater has a waterproof seal, features a ceramic heater core, and its tip is equipped with a bumper guard for extra protection and impact resistance.

The 25 watts version is suitable to mini aquariums up to 5 gallons, while the 50 watts version is suitable for aquariums up to 10 gallons.

The heater kit includes brackets with suction cup for a quick and easy installation. At 6 inches, this rod-shaped submersible heater is great if you don’t want aquarium equipment taking up space in your tank.

The heater element is made of durable, high-impact glass, designed for safe handling of the heater.

The on/off pilot light indicator allows you to monitor the operation of the heater and know when it’s working or when it’s taken out of service.


  • Temperature dial to set required temperature within predefined range (up to 78 F);
  • Impact-resistant design for extra safety;
  • Very reasonably priced;
  • Compact size.


  • Needs a thermometer.



As you’ve noticed, some of these heaters offer very good value for money, but they lack some of the bells and whistles featured by more expensive products.

All in all, I advise you to always set up a heater in your aquarium if your fish are sensitive to changing temperatures or require warmer water.

Even if you choose an affordable heater, do make sure to also get a temperature controller to avoid overheating the water.

I hope you can now pick the aquarium heater that’s best for you, keeping in mind my recommendations about getting a thermostat for some of them.

Updated: November 27, 2019
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