7 Best Mini Heaters For Small Aquariums

The cold days of winter make me feel sick; I wonder what happens to those little creatures that I own.

I am talking about my fish.


I really don’t have to worry.

As I keep myself warm, I do the same for my fish.

Warm and comfortable.

I thank aquarium heaters for that.

You can easily purchase an excellent heater for your aquarium.

How to Choose Aquarium Heater (Video)

In this article, I have listed 7 of the best mini heaters for small aquariums.

7 Best Mini Heaters for Small Aquariums

ProductsQualityWatt Requirement for Small Aquariums 
Marina Compact Heater Fully submersible10 watt
Hydor Submersible Glass Aquarium Heater - Original TheoFully submersible25 Watt
Tetra HT Submersible Aquarium Heater Fully submersible50 Watt
Cobalt Aquatics Neo-Therm Aquarium Heate Fully submersible25 Watt
Cobalt Aquatics 31020 5W Mini-Therm Heater Fully submersible5 Watt
Fluval Edge Compact Aquarium HeaterFully submersible25 Watt
Hydor 15W MINI HEATER for Bettas and AquariumsFully submersible5 Watt

Types of Heaters

Following are several types of heaters

  • Submersible heaters
  • Immersible heaters
  • Substrate heaters
  • Filter heaters

How to Choose the Appropriate Heater for Your Aquarium?

Choosing the appropriate heater for your fish tank is important.

Size is essential.

First of all:

Using a large heater to warm your small tank quickly, can cause havoc in your fish tank.

So, before making any decisions, do consider the size of your tank first, then decide upon which heater you want.

With that choose a heater which distributes the heat evenly.

Smaller tanks require a higher Watt heater as compared to larger fish tanks.

The larger the tank, the slower it releases heat.

The smaller the tank, the more quickly it will lose heat.

Mini Heater Detailed Product Description

1. Marina Compact Heater

Marina compact heater is a fully submersible heater.

The Marina C10 compact heater 10WATT is suitable for aquariums which can hold up to 10 liters or 2.65 gallons of water.

C17 is for 17 liters, and C25 is for 25 liters.

You don’t have to adjust the temperature, and the heater is designed in a way that it reaches the pre-set temperature of 78º F or 26º C.

If it’s functioning correctly, the appropriate temperature will be maintained.


Marina compact heater is suitable for saltwater as well as freshwater aquariums.

2 suction cups are available in the package which makes it easy for installation and an LED light is also attached, it shows whether the heater is on or off.

The heater will turn off when it is out of water

You can simply use a thermometer to check whether the appropriate temperature is attained or not.


  • Marina compact heater is manufactured in a way that it does not break easily.
  • A light is on when the heater is running.
  • It is Affordable
  • Easy to use


  • Sometimes marina compact heater stops working without any apparent reason
  • The heater, sometimes, switches off even when the desired temperature is not obtained which is 78º F or 26º C.
  • You can’t adjust the temperature

2. Hydor Submersible Glass Aquarium Heater – Original

Hydor submersible glass aquarium heater is not difficult to use; all you have to do is set a temperature between 67 – 91°F.

The wire of the heater is long enough.

There are different sizes of heaters for different sized aquariums.

25WATT is appropriate for small aquariums.


It can be easily fit in the small fish tank

This easy to use heater is fully submersible, and you can place it both horizontally as well as vertically.

Inside the box, you can find a manual plus suction cup.

Hydor submersible glass aquarium heater is designed in such a way that it can bear shocks without any damage to the internal mechanism.

Yes, and again you will need a good thermometer to check the temperature of the water.


  • Good for the very cold houses
  • The heater is small enough to fit in the small tank
  • The temperature on the dial is clearly written


  • Some people complain that temperature sometimes rises above the desired temperature.

3. Tetra HT Submersible Aquarium Heater With Electronic Thermostat, Cobalt Aquatics Neo-Therm Aquarium Heater

Heaters that indicate whether they are working or not are what you need.

Tetra HT heater is one of them.

A red light indicates that the heater is on and running while the green light means that the desired temperature is obtained

This fully submersible heater can be installed vertically as well as horizontally

You just have to buy a heater of the perfect size for your small aquariums.

The 50WATT tetra HT heater is suitable for 2 to 10-gallon aquarium

You don’t have to worry about adjusting the temperature, and the heater automatically maintains the temperature of 78°F which is the perfect temperature for tropical fish.

Make sure you cover the aquarium to maintain the heat inside.


  • Affordable
  • Small enough to adjust behind the decorations
  • If you keep tropical fish, then tetra HT heater is good because it maintains a temperature of 78°F


  • Sometimes the lights do not function properly
  • You can’t adjust the temperature
  • Doesn’t work well if you don’t cover the tank

4. Cobalt Aquatics Neo-Therm Aquarium Heater

I like this heater because of its different design.

It is super flat


It has an LED which displays the set and tank temperature


Cobalt Aquatics Neo-Therm Aquarium Heater is pretty unique

It has a one-touch system.

And it is small enough and fully submersible.


The product can be placed anywhere in the aquarium.

You can adjust the temperature between 66°F to 96°F.

Because of its covering, cobalt neo-therm heater does not break easily.

You can use it in a fresh water tank as well as a saltwater tank.

Thermal protection circuity in the heater shuts down the heater when needed for safety.

Upon buying the heater, you will get a warranty of 3 years.


Do read the instructions properly when using it for the first time.


  • Easy to use
  • Displays set and tank temperature
  • Temperature can be adjusted
  • Durable


  • Expensive
  • Suctions cups might stop sticking after sometime

5. Cobalt Aquatics 31020 5W Mini-Therm Heater

This product’s casing helps makes it a shatterproof heater.

Cobalt  Aquatics 31020 5W mini therm heater is fully submersible.

Its design is pretty different

There are different sizes available, for up to 5 gallons of water.

5 WATT is appropriate for 1.2-gallon aquariums.

So if you have a 1 to 1.5-gallon tank, then this heater is perfect for you.

It can be kept in all water types.


It is manufactured in a way that it distributes the heat evenly.

Cobalt 5W mini-therm heater is good for freshwater, saltwater, and terrariums.

This heater is capable of raising the temperature to 10 degrees above the room temperature.

It comes with a 3 year of warranty.


  • Affordable
  • Can also be used in 1.5-gallon tank
  • No risk of overheating


  • Reports of underheating

6. Fluval Edge Compact Aquarium Heater

This product is absolutely amazing.

You don’t have to set the temperature, and the heater reaches the preset temperature which is 78°F or 26°F.

And another thing:

The polymer exterior of the heater prevents it from getting damaged.

Fluval Edge Compact Aquarium Heater can be used in both freshwater and saltwater tanks.

The 25 WATT heater is appropriate for up to 6.6 gallons or 25 liters.

This heater is ideal for the Fluval edge aquariums.


  • Does not break easily
  • Durable


  • Temperature cannot be adjusted
  • It’s reported that the heater does not raise the temperature properly

7. Hydor 15W MINI HEATER for Bettas and Aquariums, 5-10 gal

This brilliant product is so small that it can be placed behind any decoration in the aquarium, and would not be visible to others

The heater can raise the temperature of the water, just a few degrees above the room temperature.

It raises 5°F in 5-gallon tanks.


4°F is raised in a 10-gallon tank

Hydor mini heater is suitable for marine and tropical fish


  • Heater won’t be damaged if it’s running dry
  • Great for tropical fish tanks
  • Works well in all water types


  • You cannot adjust the temperature

How Important is a Thermometer for Your Tank?

I know people who check the water temperature by simply putting a finger inside the aquarium


Whether you keep pet fish as a hobby or as a business, you have to work like a professional.

Buy a good, accurate and durable thermometer to check the water temperature of your fish tank from time to time.

Even though heaters today are designed to reach the desired temperature, but they can sometimes under heat or overheat your aquarium.

So having a good thermometer is important to keep your fish safe and to prevent them from taking a trip to fishy heaven.

So I am going to recommend you to check the temperature of your aquarium daily because you never know, even the best heater can ditch you at any moment.

If you are still using year’s old thermometer, then change it.

Yes, change it today.

Heaters and Fish

Most of the heaters in the market today adjust the temperature of your aquarium automatically, and you do not have to adjust them manually.

So the only thing you need to worry about is whether the temperature your heater is maintaining is appropriate for your fish.

Let me explain this to you:

If the preset temperature of your fish tank is 78°F, see if it’s suitable for all your fish.

Where Should I Place the Heater?

One of the most commonly asked question.

You can place the heater near the filter inlet.

 For the best result:

Install your heater horizontally.

Installing the heater vertically would also be fine

What Will Happen To Fish If They Come In Contact With The Heater?


Yes, nothing will happen to your fish.

Your fish will be just fine.

The heaters are designed in such a way, that makes them safe for the fish.

But yes…

If the tank gets too hot, your fish will eventually die to the drastic rise in temperature.

And secondly, go for a heater which does not break easily because if the heater breaks, you will surely lose your little swimmers.

Effects of the Temperature Outside the Aquarium

We all know that the temperature around the tank also affects the temperature of your aquarium.

So if you are not achieving the desired temperature of the fish tank even after placement of the heater, do not start cursing the heater directly.

First of all, check the temperature with a GOOD thermometer.

Then check the temperature of the place where the aquarium is placed.

If it’s placed in a very cold place, then you will need two heaters.

Is an Aquarium Heater Necessary?

Another great question.

So I thought I should it for those who still don’t know why it is even necessary to place the heater in the fish tank.


Why do fish die because of the cold temperature?

We humans don’t die that easily.

So here you go..

Not all fish survive in cool water, and they die when the temperature is low, and there is no heater, because they are not capable of producing their own body heat, unlike humans.



At the end take care of yourself too while taking care of the fish you own.

Do not take out the heater directly after unplugging it. Let it be cool first then take it out. Many fish lovers do burn their hands because of the careless behavior

Secondly, after installing your heater in the aquarium, plug it after a few minutes.

Related questions

Which species of fish are compatible with goldfish? Rosy barbs are one of the fish that get along well with goldfish. Loaches are suitable too because they can also survive in cool water. Goldfish are also recommended to be kept in pairs.

Do fish tanks help relieve stress? Watching the fish swimming in a well-decorated tank indeed reduces stress.

What decorations are toxic for fish tanks? There are some of the decorations which when placed in the aquarium can be harmful to you fish like plastic toys, beach sand, or any sharp decorations.

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