Aquarium Decoration

Aquarium heaters

Hi Reader, if you’ve come this far with questions like:

What are the types of aquarium heater?
How to install the fish tank heater?
Where to put it?

To have a great aquarium, you have to pay attention to many things. One of the most important is to have the right temperature for your fish and for this you need to have the correct aquarium heater.

Aquarium temperature is an important factor in the health and well-being of our fish.

Unlike humans and other mammals, fish do not produce their own body heat. They must rely on the temperature of the water to maintain their body temperature.

This makes it very important to keep the aquarium at the right temperature for your aquatic pets.

To maintain the correct temperature, one of the most used items for fish tanks is the water heater activated by one or more thermostats.

In this aquarium heater guide we are going to cover everything you need to know about aquarium heaters.

Choosing an Aquarium Heater

What is clear is that regardless of the type of heater you choose, you must have a thermometer in the tank.

Temperature control is vital to the health of your fish.

If you are just starting out in the aquarium hobby, you may try to adjust the budget as much as possible. And there are ways to cut costs, but skipping the heater isn’t one of them.

Comparison of the best aquarium heaters

Are aquarium heaters really necessary?

Temperature control

The first and most obvious use for an aquarium is for temperature control.

That said, sometimes it’s more complicated than setting the heater to 25° and that’s it. For example, some species of fish require specific temperature fluctuations to induce breeding.


Whether you have an LED lamp or a metal halide lamp that heats like hell, every light generates some level of heat.

When these lights are turned off at night, the temperature of the water can fluctuate dramatically. And if there’s one thing that’s bad for a tank, it’s temperature changes.

An aquarium heater helps keep the water temperature stable regardless of ambient temperature or lighting in the tank.


Thermostats in the aquarium hobby are typically used to turn on the aquarium heater when the temperature drops below a set minimum. Also to turn it off when the temperature reaches the set temperature.

Currently the vast majority of heaters come with their own built-in thermostat. And these actually should be called thermo-heater.

They normally have a control on the heater to adjust the thermostat and maintain the right temperature.

  • In internal heaters, the thermostat is usually integrated with a dial on the top of the device. Other models have the thermostat control on the cable.
  • There are also aquarium heaters that come with a remote thermostat that is separate from the heating element. These allow it to be placed in a different place than the heater. These devices with remote thermostats allow to maintain a more uniform and constant temperature in the aquarium.
  • There are also models that do not come with their own thermostat. These will require purchasing a separate thermostat unit to control the aquarium heater. Click here to see some examples on Amazon. These are particularly useful when the tank is in a situation where it is likely to be too cold during the winter, but too hot during the summer. With a separate thermostat, you can control both a heater aquarium as a cooler with the same device. This way you can maintain the proper aquarium temperature by using the cooler or heater as appropriate, but without the two competing with each other.

What kind of heater do you need?

Choosing the type of heater to use in your aquarium is not difficult as long as you know the differences between the different types of heaters.

There are three basic types of aquarium heaters which we are going to look at below.

Internal heater

This type of internal heater consists of a cylindrical glass, steel or titanium container with resistance inside, which is the part that is placed under water.

NEVER connect the internal heater outside the water because it heats up very quickly. You can burn yourself in addition to damaging the device.

Within the types of indoor aquariums that are placed underwater we can differentiate two classes:

Immersion heaters

Generally, the top of the immersion heater should stay above the water and can easily break if it sinks by mistake.

Immersion heaters are usually made of glass, which can pose some problems. For starters, glass is extremely brittle and susceptible to cracking. And as with anything fish tank-related, cracks are not good.

Make sure the aquarium heater fits snugly and is not resting on any stones or decorations.

Immersion heaters are generally not recommended for saltwater tanks. The corrosive nature of salt wears out many of the components in immersion heaters.

These types of internal heaters are not always efficient, sometimes not producing enough heat to work well with large aquariums.

With that said, immersion heaters are generally one of the cheapest options and are often widely used by beginning freshwater aquarium hobbyists.


  • Cheaper: You’ll find immersion heaters cheaper than most other types.
  • Silent: These types of heaters do their job in total silence.
  • Ideal for new aquarists: It is a great device for newcomers aquarists, as it helps them maintain the correct temperature of the water.


  • Not perfect for all aquariums: Hanging heaters are dangerous for marine or brackish aquariums.

Submersible heaters

They provide more flexibility, consistency, and tend to be much safer for fish. But make sure you don’t place it directly on the substrate.

This type of submersible heater is generally more efficient than immersion heaters. They are a bit more expensive, but the extra cost is definitely worth it.

Many of us have already learned that what is cheap in aquariums tends to be more expensive. Cheap equipment often ends up failing prematurely, which ends up costing more money and is also potentially dangerous.

Heaters are no exception. This is why submersible heaters are generally recommended over immersion heaters.


  • It can be placed at any angle: The best thing about the submersible heater is that they can be placed horizontally, vertically or at any angle that is needed, since they are fully submersible.
  • Internal Thermostat: Many submersible heaters have an internal thermostat, so placing the heater low enough in a horizontal position will help the thermostat get an accurate tank temperature reading.


  • Always in sight: The worst part about submersible heaters is that they must be placed inside the tank. Not only does it look horrible, but it is also a risk to fish.
  • Overheating: Submersible aquarium heaters can ineffectively heat the tank if there is not good water flow circulation.
  • Plug and unplug: Having a submersible heater is also a nuisance that needs to be turned off during every water change.

encouraging background

This type of heater is also known as heating cable or thermal heating cable. A substrate heater is what you need if you are setting up a planted aquarium. It can also be useful in freshwater aquariums to remove dead spots.

The aquarium heater will not be seen in the tank because the heating cables are hidden under the substrate and distribute heat from the bottom to the rest of the tank. This type of aquarium heater will help plants grow in just a few weeks.

One of its great advantages is that there is no need to worry about the fish damaging the aquarium heater in any way. The big disadvantage is the fact that everything has to be dismantled from the tank to install it, but also to repair or replace it.

If your aquarium is already set up or you have a lot of plants and fish, this type of heater can be difficult to install, but it may be worth the effort.

As for the price, it depends on the quality of the heater and the manufacturer, but in general these types of heaters are quite cheap.


  • Good for planted tanks: These types of heaters are ideal for planted tanks where the gravel acts as insulation keeping plant roots cool.
  • Even Heating: Substrate heaters tend to distribute heat throughout the water evenly, making for a good environment for your fish.
  • Encourage Plant Growth: Substrate heaters encourage plant growth within the tank.


  • Difficult Installation: The worst part of the substrate heater is that you need to disassemble the entire tank just to install it.

External heater

So-called «filter heaters» are relatively new to the market, but they gained popularity very quickly.

You do not have to add any accessories to the aquarium or fish tank and it will not use more energy than usual. By placing the heating device on the filter, you will heat the water while filtering it.

It is sold as the ideal solution for your aquarium, but although it seems like a great idea, the execution is not always perfect.

Depending on the configuration of the aquarium setup, it can happen that uneven heat is provided, leaving cold spots in the tank.

If you decide to buy this type of aquarium heater, it is important to pay attention to the type of filter you have, since it is possible that in old model filters there is no possibility of inserting a heating block. If you have any questions in this regard, you can see how a fish tank filter works in the previous link.


  • Hidden from view: The best thing is that you can place it outside, unlike internal heaters that need to be placed inside the tank. So all that remains is to enjoy your fish swimming freely.
  • Even and precise heating: As the heater is kept outside the tank, the water flows back into the aquarium after heating, allowing for good heat distribution.
  • No need to unplug: You can keep the aquarium heater running while you do the water change.


  • Expensive: The worst part about filter heaters is that they are twice as expensive as other heaters. If you want tropical fish inside your tank then you should set aside some budget to purchase a suitable aquarium heater.
  • No water flow, no heat: If a fault occurs with the canister filter, the water will not be pumped through the heater. The tank water temperature will drop until flow returns.
  • Risk of leaks: If you do not install the water heater correctly, there will be a risk of leaks. Therefore, care must be taken when installing the fish tank heater.

Mini heaters

Many fish that require warm water for optimal health, such as the Betta, are kept in small tanks.

These mini tanks and bowls are an absolute challenge to heat properly.

In recent years, a variety of small mini heaters have been introduced to the aquarium market.

Click on this link for another model of this type of heaters designed specifically for mini aquariums and small fish tanks.

How to install an aquarium heater

If you have a substrate heater, you can’t choose. You cannot place it where you want, as it can only be placed under the substrate.

On the other hand, there is complete freedom with the other types of heaters. In general, it is recommended to locate the water heater away from the thermostat when possible.

It is also important to place it in a place where there is good water circulation, such as next to the filter and/or in front of the water flow.

In this way, the water will heat up faster and the heat will be distributed evenly throughout the aquarium, maintaining a homogeneous temperature throughout the aquarium.

Be aware of the fact that a single heater may not be enough for your entire tank, especially if it is more than 200 litres. In this case, two heaters can be placed in different parts of the tank.

Let’s see how to put the aquarium heater step by step.

How to install an aquarium heater step by step

There are some differences depending on the heater but all heaters can generally be installed with the following steps.

  • Examine the aquarium heater before you install it. Make sure the casing is intact and there is no damage to the heating element or exposed wires.
  • Find a suitable place in your aquarium to install the heater. Make sure the glass surface in that area is clean.
  • Use the suction cups supplied by the manufacturer to fix the submersible aquarium heater in the chosen place. Make sure that plants or decorations in the aquarium do not come into direct contact with the device.
  • Wait 15-30 minutes for it to acclimatize in the water before turning it on. This allows the casing to adjust to the temperature of the surrounding water so it doesn’t crack from the sudden change in temperature.
  • Place an external thermometer on the opposite side if your tank heater doesn’t come with a thermometer to measure the temperature of the water. Look at the initial reading of the water in the tank.
  • Turn on the heater and set it to the right temperature.
  • Leave the heater running for about 24 hours before checking the temperature of the aquarium with the thermometer. Then check the aquarium heater every four to six hours and adjust the regulator until the correct temperature is reached.
  • Finally, add the fish to the aquarium. Due to the great chances of temperature fluctuation in the first few days, the aquarium heater is installed before the fish are in the tank because the change in temperature can affect the fish.

Where to place the heater

The best location to place the fish tank heater is near the flow of water. It could be at the filter inlet or outlet, or in the flow of a powerhead.

This is because water flowing directly through the heater causes heat to disperse more easily throughout the aquarium.

If you have a large tank, you may consider having two heaters placed at opposite ends of the tank. The temperature of the water will be more uniform throughout the tank, and in the event that one of the heaters fails, the other will always remain.

Heat distribution in the aquarium

There are three ways that heat can be distributed throughout the tank. These are conduction, convection, and circulation.

  • Conduction: Conduction is the typical propagation of heat towards cold to achieve thermal equilibrium. When water gets hotter, the water molecules get more kinetic energy and start bouncing around more and this heat energy spreads throughout the water. Water is a decent conductor of heat, but most of the heat distribution in your tank will be by convection and circulation.
  • Convection: Convection occurs when heated water becomes less dense and rises to the top creating what are called convection currents. When the heater heats the water, it rises to the top to be replaced by cooler water.
  • Circulation: The primary vehicle for heat transfer in your aquarium will be from your filter’s circulation. Ideally, the filter mixes the water well to avoid hot or cold spots.

Other suggestions regarding the placement of the heater

We have already discussed the usual way to distribute heat throughout the tank is to have the aquarium heater near the filter inlet. The hot water will be sucked through the filter inlet along with cooler water from the bottom of the aquarium.

Some experts suggest placing a submersible heater horizontally on top of the gravel next to the filter outlet. In this way, the heater works with the hot zone surrounding the device with the circulating water of the tank.

Other aquarists suggest placing an air stone under the aquarium water heater. This pushes the denser cold water that is in the lower part upwards, towards the heater facilitating the uniform distribution of the water temperature.

Relation between volume of the aquarium and the heater

Not sure what size heater you need for your aquarium?

The power or size of the fish tank heater depends fundamentally on the difference in temperature between the water in the aquarium and the room. Keep in mind that the filtering and lighting system provide heat.

There is a general way to calculate the proper heater size, based on the temperature of the room and the volume of water in the tank.

As a general rule, many consider that the ratio liters – Watts of the aquarium heater is sufficient, that is, that the aquarium has as many Watts as liters. 100 liters of aquarium, 100 Watts of heater.

Others believe that it is better to have a 1.5W/1L ratio, that is, 100 liters, 150w heater. This would avoid continuous operation of the device in the coldest seasons.

It should never have more than twice as many Watts as liters, nor less than half as many Watts as liters.

These rules are valid to have a generic idea. Because a 100-litre aquarium in the north of Spain is not the same as in the south. For this reason, the temperature difference between the water in the tank and the room must also be taken into account.

It is necessary to set the temperature of the room and the desired temperature of the tank.

First, subtract the average temperature of the room in which the aquarium is located from the appropriate temperature to keep the aquarium water at.


  • Room ambient temperature = 18ºC
  • Suitable aquarium temperature = 23ºC
  • Heating required = 5ºC

We are going to see an indicative table that relates the Watts necessary to increase the temperature of a tank of a certain size by a few degrees.

Relationship between water temperature, aquarium size and heater Watts
Aquarium Size Increase 5ºC Increase 7.5ºC Increase 10ºC Increase 15ºC
25 liters 25W + 5ºC 50W + 7.5ºC 50W + 10ºC 75W + 15ºC
50 liters 50W + 5ºC 75W + 7.5ºC 75W + 10ºC 100W + 15ºC
75 liters 75W + 5ºC 75W + 7.5ºC 100W + 10ºC 150W + 15ºC
100 liters 75W + 5ºC 100W + 7.5ºC 100W + 10ºC 150W + 15ºC
150 liters 100W + 5ºC 150W + 7.5ºC 150W + 10ºC 200W + 15ºC
200 liters 150W + 5ºC 200W + 7.5ºC 200W + 10ºC 300W + 15ºC
250 liters 200W + 5ºC 250W + 7.5ºC 250W + 10ºC 200W x 2 + 15ºC
300 liters 250W + 5ºC 300W + 7.5ºC 300W + 10ºC 250W x 2 + 15ºC

Finally, we have to take into account when choosing the size of our heater:

  • If we choose a heater that is too small, it would always be working, shortening its useful life and increasing the electricity bill.
  • If we choose one that is too large, it could heat the water too quickly, harming the fish.

How much electricity does an aquarium heater use?

Heating an aquarium has a price that depends on the size of the tank. The larger the tank, the more heat is needed and the more expensive it will be.

Also, a tropical environment for fish generally requires higher water temperatures, which means more electricity and more money.

In general, there is no way to provide an exact amount of how much it will cost to connect a heater to the aquarium. But with the size of your tank and the temperature needed, some estimation can be made based on the information provided in this article.

How to choose the right aquarium heater

Aquarium Heater Size

The first thing to look at is the size of the tank before deciding which aquarium heater to buy.

Each aquarium heater manufacturer will state what size tank each model will be best for.

The aquarium heater has to be powerful enough to deliver the performance that the tank needs when it comes to heating the aquarium. It has to have enough power so that the water does not take too long to reach the right temperature.

Type of aquarium

You should also always consider what type of aquarium you have before deciding which aquarium heater to buy.

The manufacturer always offers all the information in the description about where the aquarium heater can be used. Rest assured that you will find heaters for saltwater aquariums, freshwater aquariums, turtle tanks, betta tanks and reef tanks.

It is also possible to find models that will work in various types of aquariums. A versatile option is always going to be a good option.

Type of aquarium heater

We have seen that there are currently several types of heaters. Options include submersible, filter and substrate heaters.

As long as you buy the right fish tank heater, you can be sure that any of them will deliver great performance.

It is necessary to understand how each type of heater works before making a decision.

Ease of maintenance

At some point, you will have to deal with the issue of maintenance. It all comes down to how easy it is to keep the heater in good working order.

Choose a model that is easy to clean. The same goes for how easy it is to replace any broken or worn parts.


The last thing to consider is the amount of money you are willing to spend.

Sometimes the budget determines what heater one can afford. But with a little research, you can get the best aquarium heater for your budget.

What is the best aquarium heater?

The list of the best aquarium heaters on the market right now:

  • fluval E
  • Tetra HT
  • Neo-Therm Aquarium Heater
  • Aqueon Pro Heater
  • EHEIM Jager
  • hydor In-Line

These heaters are made to meet the standards of most aquarists. They always offer performance, durability and impressive heating capacity.

As much as they are all excellent, the best possible choice for many would be the fluval E Advanced electronic heater.

This type of heater offers some of the best features available, such as better heating capacity and accurate temperature reading.

It’s also built with the security features you need to make sure you stay happy with your purchase for a long time.

Aquarium Heater Tips

On many occasions it is advisable to use two smaller heaters located in opposite places to distribute the temperature in a more homogeneous way, and also if one fails we have the other.

To be ready for any unforeseen event, it is advisable to have a spare heater in case the current one breaks. If it can’t be replaced for a few hours, your fish could be in big trouble.

There is a trend that uses bottom heaters to increase the temperature of the substrate and promote plant growth.

If you discover some type of imbalance in the temperature of the aquarium water, when correcting the deviation, do not cause sudden changes, and do so gradually.

Although the heater is not an essential device in all aquariums, I recommend its use to maintain a stable temperature.

If the heater can only be partially submerged, it would be a good idea to put an air stone under it to help circulate the hot and cold water.

A fully submersible heater is always better than a partially submersible one. This gives the hobbyist more freedom of placement for whatever heating position the situation calls for in a single aquarium setup.

Some submersible heaters don’t last as long if installed horizontally, but it’s probably a good idea to replace most heaters once a year.
In this way, a catastrophe with a malfunctioning heater is less likely to occur and a failure is prevented before it occurs.


For this reason it is necessary to provide adequate heat to the aquarium to keep it at the correct temperature for your fish.

And choosing the right aquarium heater for each tank has «more crumb» than it may seem at first.

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