10 Best Aquarium Heaters Buyers Guide 2021

Aquarium Heaters

If you are already passionate about keeping fish, I am sure you are familiar with the importance of an aquarium water heating system.

But if you’re a beginner, you probably don’t really know what to buy, particularly if you aren’t familiar with what parameters to consider. Lots of people just look at the cost of the heaters, and try to find the cheapest one.

Other people spend hours doing research, trying to be certain that they choose the right one. We have prepared this guide to help you make the right choice.

Recommended Fish Tank Heaters

  1. Tetra Ht Submersible Aquarium Heater
  2. NICREW Submersible Aquarium Heater
  3. Fluval E 100-Watt Electronic Heater
  4. Hygger Submersible Aquarium Heater
  5. Hydor In-Line External Heater

Things to Consider Before Buying a Heater for Your Fish Tank

Installation Location: Aquarium heaters can be installed in different positions. They can be immersed, submerged or mounted on the filter.

The immersion model is probably the most affordable. However, the control knob has to be permanently placed above the water level, and setting the right temperature is sometimes difficult. As they are quite cheap, it’s a good idea for a beginner to purchase a more advanced model, or keep one of these as a backup solution in case your system fails.

The submersible model is somewhat more expensive, but it can be placed entirely underwater. The heating cables are positioned in the substrate, providing a more uniform effect than other types of heaters. As they are almost completely hidden, they don’t spoil the overall look of the aquarium.

Submersible heaters are a good solution for aquarists who love natural plants, as they keep the water temperature constant. However, if there is a problem with the heater, it’s necessary to dismantle the whole aquarium to get to the heater. Clearly this is not very convenient!

The latest and most efficient heating solution is provided by filter heaters that adjust the water temperature as the water is filtered. Again, they don’t affect the overall look of the aquarium and it means you don’t need an extra piece of equipment in the aquarium. However, many buyers are put off by the fact that they are quite expensive.

Heating Power: This should be decided by looking at your aquarium parameters. What temperature does the water need to be kept at? How many degrees is this above your room’s usual temperature? What is the water capacity of your aquarium?

There are charts available that will help you to choose. As a rule of thumb, a small tank that needs heating by just a few degrees will need a smaller heater than a large tank that needs significant heating. Heaters are available with power ranging from 25w to 300w.

If you are not sure which heater to get, then opt for the strongest one. If the aquarium needs to be set at an unusually high temperature, or is in an unusually cold room, it might be an idea to buy two devices that can be placed at opposite ends of the container.

An exception to this relates to mini-heaters: they are suitable, for example, for small bowls containing Betta fish. With power between 7.5w and 15w, they are submersible and can be placed on the side of the aquarium or on the bottom of the aquarium beneath the gravel.

Material: Traditionally, heaters are made of glass, but many fish-keepers do not like this, particularly if they are keeping large, or especially energetic fish, as there is a risk that they will break. This is why strong plastic or very thick glass heaters are sometimes preferred.

Location: There is plenty of controversy about where the heater should be placed inside the aquarium. Some specialists say the best position is near the filter, where water circulation is more intense, meaning that temperature will be more quickly equalized.

Other aquarium specialists will advise you to opt for an under-gravel position wherever possible, as hot water will climb to the surface, while cold water will come down and heat up in turn.

If your fish enjoy a very generously sized aquarium of over 150 liters, maximum efficiency will be achieved by placing two heaters, one at each end of the aquarium. Other aquarists prefer to opt for two small capacity heaters, instead of a large one, even for slightly smaller spaces.

Maintenance and Cleaning: Although modern aquariums no longer need to be cleaned as often as they once were, cleaning should still be done periodically. Therefore, to reduce effort and time, we advise you to choose an easy-to-clean heater that requires minimal maintenance.

Other Features: If you have extremely precious or very sensitive fish, it is advisable to purchase a top-quality heater that includes the additional function of a thermometer and/or thermostat. If they are digitally controlled, you know that you can really trust them!

Price: Contrary to general opinion, keeping fish is not a very cheap hobby. So it’s not a bad idea to ask around other aquarists to find out where to find an aquarium heater at a good price.

List of Best Aquarium Heaters

You can generally get a better deal online, rather than going to specialist shops. They will have the same products, and in fact are likely to offer more variety. It’s certainly more convenient to order what you need form the comfort of your own home.

1. Tetra Ht Submersible Aquarium Heater With Electronic Thermostat

The Tetra HT Submersible Aquarium Heater with an electronic thermostat is easily one of the most popular aquarium heaters on the market. This heater can accommodate tanks up to 30 gallons, and is available in 50w and 100w sizes. This Aquarium Heater for small aquariums is completely water-resistant and perfectly sized. It can also be installed vertically or horizontally so that you can put it anywhere.

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The Electronic Thermostat Tetra HT Submersible Aquarium Heater features an inbuilt electronic thermostat which automatically maintains a temperature of 78°F, ideal for most tropical fish. The heater also has an indicator light that allows you to know when it’s activated, when the desired temperature is reached (green) and when the water is being heated (red).

2. NICREW Submersible Aquarium heater

This completely submerged heater has a touch control system and a sleek and slender design that will suit even the most stylish home. The heater is equipped with an LED that shows both the heater temperature and the tank temperature. You can adjust the temperature to between 66°F and 96°F.

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The thermal circuit is integrated and shuts down the heater before it can overheat, and it is contained in a scratchproof case that makes the heater virtually indestructible. Depending on your tank’s size and your heating requirements, it comes in a range of sizes from 25 watts to 250 watts.

3. Fluval E 100-Watt Electronic Heater

The Fluval E series of heaters is equipped with a Celsius or Fahrenheit temperature display. They are fully immersed and are equipped with an alarm to change the color of the LED to indicate when the temperature differs from the preset temperature.

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The heater comes with a built-in fish guard that protects your fish against heat. These heaters come in a variety of wattages that are suitable for a wide range of tank sizes.

4. Hygger Submersible Aquarium Heater

In this line of heaters from Hydor, the Original Theo is the smallest. The control button is marked with increments of one degree and can be set precisely. The heater body length is short enough for it to be accommodated in small 2.5 gallon tanks. Its body is shatter resistant and shockproof, and the light indicator lets users know when the heater is in operation.

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This heater can be installed in the fish tank either horizontally or vertically. The length (at just seven inches) makes it ideal for tanks smaller than 10 gallons.

5. Hydor In-Line External Heater – Original ETH

The filter is an external, tropical as well as marine thermal heater. It can be used only vertically, however, although it is easy to connect and use. It was designed for the return line from canister filters or buckets, heating the water on the way back to the tank.

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The positive thermal coefficient (PTC) technology ensures self-heating and blowing. It comes with piping between 12mm-16 mm and it has temperature control for easy vision, depending on the size you want.

6. Cobalt Aquatics Neo-Therm Aquarium Heater

You can set the temperature range between 66°F and 96°F and keep the water temperature within 0.5°F. This heater has a modern, super flat design, which complements any tank.

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Easy to access, the “one-touch” control system displays both the set temperature and the current tank temperature with LEDs. The heater is completely submerged and shatterproof, so there are no cracked glass concerns.

7. Eheim Jager Aquarium Thermostat Heater

Because of its size, this heater may need to be placed horizontally in your tank. If this is placed vertically, the length can be a major bonus, since the dial is very close to the surface, making it very easy to set the thermostat.

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The TruTemp dial has an easy setting function that enables you to set the temperature you want; and it keeps the temperature within 0.5°F. However, you will have to repeat the calibration procedure a few days after the initial configuration. The handy light on / off makes it easy to monitor whether or not the heater works.

8. Hydor Submersible Glass Aquarium Heater – Original Theo

This is an inexpensive, good aquarium heater and we thoroughly recommend it. Its efficiency is due to patented PTC technology – positive thermal coefficient – which makes its use perfectly safe. The heating is achieved by means of a specially coated element on which a graphite ink layer has been applied.

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The 300w power makes it suitable for aquariums up to 200-300 liters; for larger capacities, you can purchase two such products, as the integrated thermostat will take care to maintain the water temperature at optimum values and to minimize power consumption. In addition, the built-in thermostat makes it extremely precise in temperature adjustment.

9. Aqueon Pro Heaters Submersible Aquarium Heaters

The Aquarium Heater is a state-of-the-art aquarium heater, accurately equipped with a first-grade electronic thermostat, with a wide temperature range from 68°F to 88°F. This aquarium heater has a shatterproof construction and is completely submersible for durability. Place the heater in the tank near the filter outlet for even heat distribution.

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In addition to being very precise and adjustable within 1 degree, the Aqueon Pro Adjustable Aquarium Heater provides several security features. It automatically protects against overheating and resets when it cools down. The red LED activates the heater when the water temperature falls below the desired setting, and the light turns green if the temperature reaches the desired level.

10. SZELAM 25W Smart Mini Aquarium Heater, Betta Fish Tank Heater

A small heater that is suitable for small tanks and betta tanks. It can be efficient in tanks up to 6 gallons due to its 25W power. It has a thermostat that automatically switches on and off when the temperature reaches its optimal range.

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On the down side, the units tend to fail after a while, making it not very reliable. This is why it landed in last place on our list.

Practical Tips for Using an Aquarium Heater

Remove the heater from the socket at least 10 minutes before replacing the water. Warm glass cracks gently when subjected to high fluctuations in temperature. In addition, there is a risk of burning your hand. In the same way, never insert a heated or connected appliance into the cold water.

Place the internal heaters in the vicinity of the filters or pumps. Currents provide better circulation of heated water inside the aquarium.

It’s not impossible for the heater thermostat to fail, so it’s a good idea to install a separate aquarium thermometer to check for overheating.

Fix the internal heaters with suction cups. Most come with these, but if it doesn’t then it’s very easy to buy some. Unfixed heaters can hit the aquarium walls and break.

Place fully submersible heaters on the bottom of the aquarium in a horizontal position so that warm water rises to the surface and heats up the whole water column.

More important facts about aquarium heaters:

Some submersible heaters do not have a thermostat, so you will need a separate thermometer to indicate the temperature in the aquarium. And you will need to keep an eye on this thermometer and turn off the heater when the water has reached the desired temperature. The price difference between this type of heater and the ones listed above does not warrant the extra effort or the risk of over-heating your tank.

Substrate heaters: These have been around for a long time, but they aren’t very popular. As the name suggests, put them on the bottom of the aquarium under sand and/or gravel and heat the aquarium efficiently from the bottom up with convection currents.

One big advantage is that it ensures a higher temperature in the substrate (favoring plant development), which does not happen with the other types of heaters.

However, they do not have a thermostat, so they’re harder to control. In addition, if they are not put in place right at the start of the setup, you can’t add them later.

External heaters: They are more expensive than the above but more accurate and efficient. They can be either in-line or directly attached to the filter system.

The big advantage is that it they do not occupy space in the aquarium and there is no risk that the fish will burn or damage the heater (some cyclists attack the aquarium installations). The in-line is attached to the aquarium water return through a tube system. How extra piping attaches increases the risk of leakage or flooding.

Filtering systems that have an integrated heater are excellent. They are practical and reliable, but very expensive. When water passes through the filter it is also heated. They have a thermostat, and the temperature can be easily adjusted.

It is a compact, easy-to-use system. Heated water returns directly into the aquarium, and with the pumping system, it is rapidly mixed with the existing water. A negative aspect is that if the heater or filter fails, the whole system needs to be changed.

DIY Aquarium Heater – Is it worth it?

When making a heater, remember there is electricity involved and this might make it dangerous.

But if you do decide to make it yourself, then you can make one using a resistor, a piece of thick wall glass tubing, dry filler and an external thermostat. Installation work should be done in the following order.

The power of the heating element is determined on the basis of a special table (see below), which takes into account the temperature difference between the room air temperature and the required water temperature.

By dividing the voltage used by the calculated value of the current, you can obtain the resistance value of the heater. The required number of identical resistors is selected so that the total power and resistance index corresponds to the calculated values.

  • Determine the length and diameter of the glass tube according to the calculated resistance.
  • It is important that successive glued resistors are placed in the tube with a spare 15 cm of free space.
  • You can use calcined sand as a filler.
  • The bottom of the glass tube is closed with a suitable rubber stopper and sealed with aquarium sealant.
  • The ends of the mains cable are glued to the top and bottom resistors. The entire structure is placed in the tube and covered with sand.
  • The end of the tube is carefully closed with aquarium sealants. The power cable is connected to the thermostat with a remote temperature sensor, which in turn is located in the aquarium.
  • The heater is placed vertically, so that the part of the tube in which the resistors are located is hidden underwater. It should then be mounted on the aquarium wall with special suction cups.

Related Questions

How many watts does my aquarium heater need to be?

Depending on the size of the tank, aquarium heaters can range from 5W up to 500W. If you have a small tank, such as a betta tank or something up to 10 gallons, a 30W heater will do the job right.

But putting a 30w heater in a bigger tank will not work as only the water near the heater will be heated, and not the rest of the tank. For bigger tanks, it is recommended that you get a heater with a bigger power range, such as a 100w or 200w one.

Keep in mind that there are aquarium heaters that allow you to switch the power range, they are a bit expensive but they tend to be more versatile and can be swapped from one tank to another.

Tank Size 5 Degrees C

9 Degrees F

10 Degrees C

18 Degrees F

15 Degrees C

27 Degrees F

5 Gallon/25 Liter 25 watt 50 watt 75 watt
10 Gallon/50 Liter 50 watt 75 watt 75 watt
20 Gallon/75 Liter 50 watt 75 watt 150 watt
25 Gallon/100 Liter 75 watt 100 watt 200 watt
40 Gallon/150 Liter 100 watt 150 watt 300 watt
50 Gallon/200 Liter 150 watt 200 watt two 200 watt
65 Gallon/250 Liter 200 watt 250 watt two 250 watt
75 Gallon/300 Liter 250 watt 300 watt two 300 watt

What kind of fish need a heater?

All types of aquarium fish require the water to be above 35°F. It is important to keep the water warm as fish kept in cold water will become lethargic and may eventually die.

On the other hand, keeping fish in water that is too hot will have the same effect. Having an optimal temperature range is important.

You can refer to your fish data chart to learn more about their optimal temperature range.

How much do fish tank heaters cost?

The price of aquarium heaters varies, depending on their features, their build quality and the brand.

While in most cases, having a product from a known and well-established brand can be a good choice because of the excellent build quality and warranty period they offer, some cheaper brands can work just fine, especially if you are on a tight budget.

You need to stay away from dodgy looking heating units, these tend to have a very poor build quality and they will break quickly, increasing the risk of injury or worse.

Where should I place the heater in my fish tank?

This depends on the type of heater you are using. Most heaters are made so that they can be placed on the aquarium wall.

A good practice is to place the aquarium heater near the water filter or the skimmer so that the water that gets heated can be dispersed through the aquarium, bringing the whole tank to an optimal temperature.

Can you put two heaters in a fish tank?

Yes. This is a common practice among aquarists who own large aquariums. Placing two heaters on opposite sides of the tank will make the water heat up more quickly, and will also heat a larger volume of water.

But keep in mind, don’t place the heaters very close to one another since this will confuse their thermostats, and the result will probably be poorly heated water.

Saurabh Kumar

I am a passionate fish keeper, with years of experience. You will find some really useful tips and information on this blog about Freshwater Aquariums.

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