Best Small Aquarium Heater: Top 5 To Keep Your Buddies Warm

Best Small Aquarium Heater: Top 5 To Keep Your Buddies Warm

11 min read

If you have a small aquarium in your home, it is increasingly important to maintain a constant temperature. Because small aquariums have less volume of water, they are more suspectable to fluctuations when compared to large aquariums. Some small aquariums have nano tanks that are suited for small-scale inhabitants. These aquariums require nano aquarium heaters.

So you should pick the perfect aquarium heater that is made for the aquarium size that you have at your home. That's why we decided to have an in-depth go at it to find the best small aquarium heater for you.

Most small aquarium owners do not have the inclination, time, or money to purchase various aquarium heaters for trial and error and settle on one.

So, we decided to give you the best understanding of it and shortlist the best small aquarium heaters that would be reliable for you and keep your aquarium at a consistent temperature for a long time to come.

How We've Selected The Best Small Aquarium Heater

A suitable price range for good small aquarium heaters is up to $50. With this budget in mind, we divided it into three segments. At the lowest end, we looked for the most compact-sized aquarium heaters. These heaters offered adjustability and were durable and reliable. In the mid-budget range, we looked for small aquarium heaters that weren't only better in adjustability, reliability, and durability but also made out of the best material. At the highest end, we looked for the best small aquarium heaters that your money can buy.

We were able to narrow down the aquarium heaters in accordance with the customer reviews. We selected the ones which were most trusted by the customers and had an overall good rating. Finally, we shortlisted the five best small aquarium heaters that we will now review.

5 Best Small Aquarium Heaters

1. FREESEA Aquarium Heater

Why We Love It

Freesea is one of the most trusted and recognized brands in the aquarium heater market. Not only does it provide professional after-sale service, but it is also majorly focused on product optimization and innovation, which enables it to provide stable and high-quality aquarium supplies.

A Freesea aquarium heater is one that you can always rely on to keep your fish healthy and safe. It is a highly adjustable aquarium heater that enables easy monitoring of the water temperature, ensuring that the conditions remain optimal inside the aquarium. So, whether your fish prefers a cold or a warmer temperature, your ability to frequently monitor the temperature on its LED temperature display will eliminate all your worries.

Before buying a FREESEA aquarium heater, you must know how many watts of power your small aquarium heater require depending on its size and the volume of water in terms of gallons. If your small aquarium has a 1 to 5-gallon tank with a length of around 6.8 inches, it would require the aquarium heater to have 25 watts and a 4 feet long power cord, and a voltage between 110 to 120.

If you found the above calculations confusing, Freesea provides a size chart that allows you to choose the correct wattage aquarium heater according to the size of your aquarium.

The FREESEA aquarium heater also comes with a free thermometer that allows one to observe the temperature of the water at any time. The heater also has a very efficient temperature control function that enables it to automatically shut off when the water temperature reaches a specific point and it would begin heating again when the temperature drops to a certain below point. It also includes overheating protection and features an automatic safety shut-off.

The Freesea aquarium heater comes with a 12-month warranty. If you are unsatisfied or find a genuine problem with your small aquarium heater, Freesea will replace it and give you a new one.

What You Should Know

When cleaning the fish tank, ensure to unplug the power supply for safety reasons. Also, be sure to submerge the heater inside the water completely. It is also preferred that without adult guidance or supervision, Children or minors should not be allowed to work, adjust or be near the heater rod.

2. Tetra HT Submersible Small Aquarium Heater

Why We Love It

The Terra HT small aquarium heater is a highly reliable, cost-effective aquarium heater. It comes with indicator lights, so you never miss when the upper limit water temperature has been reached (which is when it stops heating) or when the heating is on. The green signal indicates that the water has reached the desired temperature. The red light indicates that the heater is on and heating.

It has the ability to automatically maintain water at 78 degrees without any adjustments, as it comes with a built-in electronic thermostat making it ideal for most tropical fishes.

It can easily be concealed behind decors or plants because of its small footprints and the fact that it can be installed horizontally and vertically. It is also fully submersible and is an ideal pick for aquariums with glass canopies or hoods between 2 to 10 gallon tanks. However, you do have the option of buying a higher-watt heater for larger tanks.

What You Should Know

When you make the purchase, be sure to choose the right heater according to the size of your tank. People sometimes end up buying a heater that turns out to be too small for their tank, which causes underheating.

You'll also have to ensure that heating is concealed inside the aquarium. You can do this by ensuring that the tank is equipped with a glass canopy or a hood.

3. Marineland Precision Small Aquarium Heater

Why We Love It

The Marineland precision aquarium heater comes in different power options that range from 50 to 400 watts. It allows an easy way to set the temperature as it comes with an adjustable temperature dial that, with every click, changes a degree. It has an automatic thermal switch that monitors the temperature, turning off as it rises above the set range and turning back on as it cools down.

It offers exceptional heat transfer making it highly durable because of its advanced heating element consisting of a mica core surrounded by a mesh heating element.

Marineland precision heater makes it easy to view temperature as it comes with an advanced mounting bracket that attaches to glass securely, providing three window positions to view from.

It has a top dial view and sliding scale that is very easy to operate, so you always know the exact temperature and the setting for an additional location.

What You Should Know

Be sure to use a tank cover to prevent water level variances and heat loss since any of these cases can hinder the heater's performance, causing a hazardous environment for the fish.

4. Penn-Plax Small Aquarium Heater

Why We Love It

The Penn-Plax small aquarium heater is a fully submersible small aquarium heater. Its red control knob allows you to set the temperature anywhere between 68 degrees and 89 degrees, ensuring easy maintenance of water temperature that is healthy within a 1-degree accuracy.

The temperature settings are very easy to view because of their setting scale, which allows you to view the temperature in Celsius and Fahrenheit. Rotate the control knob clockwise if you want to decrease the temperature and rotate it counterclockwise if you wish to increase it. You can also use the negative and positive signals located near the control knob.

Moreover, you'll always be aware of the heating cycle status as this small aquarium heater features a pilot light that works as an indicator. This means that it will automatically turn off and turn on as the thermostat cycles the heating element off and on. So, if the heater is on, it will show an orange light, and when turned off, it will make a faint click.

You can place this fully submersible heater vertically and horizontally. It is also composed of shock-resistant and heavy-duty glass. At the top, you'll find a red-colored, built-in minimum water level indicator.

What You Should Know

Be sure to position the suction cups within the top levels of the heater, as you wouldn't want them to be in any kind of contact with the heater element region at the lower half of the heater.

5. Marina Betta Small Aquarium Heater

Why We Love It

The Marina Betta heater is one of our most reliable and durable picks. It is a submersible, automatic fish tank heater that provides the ideal conditions for your fish to thrive. Compared to glass sleeve heaters that are more traditional, it is much more resilient as the exterior is made of durable polymer.

This 8-watt submersible fish tank heater can heat up a 1.5-gallon tank. You won't need to make any manual adjustments as it's designed to maintain and reach a set temperature for your fish tank's water.

A red indicator light indicates that the heater is on or heating. A suction cup that comes with it which can be installed easily against the aquarium's window.

What You Should Know

There have been a few rare cases when the automatic water temperature monitoring feature of the Marina Betta small aquarium heater has failed to work, turning it into an "always on the heater."

How To Choose The Best Small Aquarium Heater

Most new small aquarium owners usually do not understand its sensitivities until they face the consequences, such as a fish dying due to lack of or no warmth in the water. Most tropical fish do not do well in cold water.

Hence, you can not think of not getting or skipping the purchase of a small aquarium heater. There's also the usual issue of not having enough space to adjust for a heater in your small-sized aquarium, especially after you are done with all the decorations, such as rocks, plants, and gravel.

Many people also complain that the water does not get warm enough even after they install the heater inside the aquarium.

If you want to avoid any of this happening, you should understand the tank's size, room temperature, and the temperature you'd like to raise your aquarium water.

It is also important to understand the aquarium heater's "power" measured in watts. Higher the number of watts, the higher the power the heater generates. For example, a 10-watt heater would be two times as powerful as a 5-watt one.

Adjustable Aquarium Heater

An adjustable small aquarium heater is one that regulates the temperature of the aquarium in accordance with the average room temperature. How it functions is that instead of staying "always on" (which is the case of the majority of the small aquarium heaters), it automatically turns off when a temperature limit is achieved (typically around 26 degrees Celsius) and turns on again when the temperature reaches the lower limit.

However, you may find that adjustable aquarium heaters are comparatively larger than non-adjustable aquarium heaters.

Non-Adjustable Aquarium Heaters

Unlike an adjustable heater, a non-adjustable aquarium heater is "always on" and never shuts off, regardless of how hot or cold the water is and what the room temperature might be.

Their inability to regulate the water temperature leaves you and your fish/fishes at the mercy of the heater. Even on the hottest of days, this particular heater type would not automatically shut down, and this could literally cook your fish. So, it really doesn't matter whether your fish prefers cooler or warmer water.

However, there is a solution to it in the form of an aquarium temperature controller. It is a device that can keep your fish safe as it turns the heater off when the water gets too hot and turns it back on again when it drops to a cooler temperature.

Moreover, with all things said and considered, a big advantage of non-adjustable aquarium heaters is their small and slim size, allowing them to fit in really compact aquariums. This also leaves you with plenty of space to decorate the aquarium as you may like.

The Size of the Small Aquarium Heater

The size of the small aquarium heater is one of the most important decisions you will make. If the size is too big, it would often end up overheating the aquarium. If it is too small, it won't be able to deliver as much heat as needed.

It all depends on the power of the heater. The volume of water in your aquarium will determine how many watts will be needed to keep the water warm enough without over or underheating.

An aquarium that has 5 gallons of water will need 25 to 50 watts, while a 10-gallon tank will need 50 to 100 watts.


Another thing to consider when choosing the best small aquarium heater is its material.

If you go for glass, it'll cost you less compared to acrylic. Yet, acrylic is a much better insulator compared to glass. Because it is also easy to install, acrylic goes really well with small aquariums.

A substrate heater is placed under the substrate in the aquarium. Easy to use and install, the substrate heaters are small in size with coils of wires that heat up when turned on, radiating heat from the heated wires to the gravel, which further transfers that heat to the water.


It's essential to place your small aquarium heater in the perfect spot. Sometimes aquarium heaters end up damaging or even shattering the glass. So, you'll have to ensure the heater never comes in contact with the glass.

Also, you should pick a place where it delivers the optimal level of heat throughout the aquarium without compromising on decorations.

Frequently Asked Questions about Small Aquarium Heaters

Here are the most frequently asked questions about aquarium heaters.

What size heater do I need?

The most important factor for selecting an aquarium heater is size. You want to ensure that the heater is large enough to warm your tank but not so large that it overheats. The general rule of thumb is that you want a wattage of 2-5 watts per gallon of water in your tank. So, if you have a 10-gallon tank, you would need an aquarium heater with at least 20 watts of power.

Should I get a submersible or non-submersible heater?

Generally speaking, submersible heaters are easier to install and maintain, and they provide more even heat distribution throughout the entire tank. Non-submersible heaters are typically cheaper and simpler to use. Yet, they tend to be less efficient regarding energy consumption. Ultimately, it's up to you which type of heater you choose – ensure that it meets all safety requirements for your particular fish tank setup.

How can I make sure the temperature is steady in my tank?

Once you've selected the right size and type of aquarium heater, the next step is to ensure that it keeps the temperature in your tank steady and consistent. To do this, you should invest in an aquarium thermometer to monitor the temperature at all times. Additionally, many modern aquarium heaters come with built-in thermostats, which automatically adjust the temperature as needed based on preset temperatures that you can set yourself!

What is the smallest aquarium heater?

Freesea offers aquarium heaters that are as small as it gets - perfect for tanks of all sizes, from 1 to 5 gallons. Keep your fishy friends warm and comfy with these mini-heaters.

How do I keep my small aquarium warm?

There are a few ways to keep your small aquarium warm. One way is to use an aquarium heater. Another way is to place the aquarium near a heat source, such as a radiator.

Do small fish tanks need heaters?

Not all fish thrive at the same temperature. Tropical varieties need extra TLC to stay comfortable, so be sure to invest in a heater for your small tank if you're planning to add any of these happy swimmers.

Final Remarks

Selecting the best small aquarium heater for your tank doesn't have to be complicated.

By following our advice – understanding what size and type of heater work best for your particular setup, investing in an aquarium thermometer, and opting for a model with an adjustable thermostat – choosing an appropriate small aquarium heater should be easy.

Thanks for reading!

Items reviewed:

1. FREESEA Aquarium Heater

2. Tetra HT Submersible Small Aquarium Heater

3. Marineland Precision Small Aquarium Heater

4. Penn-Plax Small Aquarium Heater

5. Marina Betta Small Aquarium Heater

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