Whether you have an aquarium or a terrarium, having a thermal heater is very important, especially when you have tropical fishes.

There are many types of heaters available at stores, such as submersible, semi-submersible, and external ones.

However, the submersible ones end up cluttering the aquarium and, at times, do not maintain constant water temperature. In contrast, the semi-submersible ones, which float in the aquarium, may not be very pleasing to look at.

Therefore, in this Hydor Inline Heater review, we will talk about an external thermal heater that will not only help in achieving a constant water temperature but will also be aesthetically pleasing as well.

Hydor Inline Heater Review
Hydor Inline External Heater

Things to Consider Before Buying

Aquatic life must be kept at a particular temperature to survive. If the temperature of the water drops below 78 degrees, then this may end up killing the fishes. This is why having the Hydor In-line external heater will come in handy.

·      Not water resistant

If you are looking for a submersible or semi-submersible water heater, then this isn’t the gadget for you. The device is not waterproof and, therefore, shouldn’t be immersed in water.

So, when you are installing the heater, you need to make sure that the valve taps are properly closed off. Water seeping in through the taps can cause damage to the device.

Also, when you are cutting the external pipe during installation, you need to make sure that the water in the pipeline is completely emptied.

Furthermore, after installing the heater, you may have to keep an eye out for any air bubbles trapped in the pipes, as these can also ruin the product.

·      Choosing the right power and size


These heaters are available in two different power models, namely, 200 watts and 300 watts. The 200-watt power models are suitable for heating tanks that can hold water between the range of 100- 200 liters, and the 300 watts model is best for tanks with a range of 180- 300 liters.

The heaters also come in different hose pipe sizes, such as 1/2inches and 5/8 inches. These sizes are available for both the 200 watt and the 300-watt models.

In this way, you have the freedom to choose the model that is best suited for your aquarium effortlessly with customization based on the size of the tanks and pipe.

Apart from all that, consider buying a controller for your aquarium heater to be always in the safe side.

Presenting Hydor In-line External Heater

For those looking for a heater that does not require constant maintenance, then the Hydor In-line External Heater is your go-to. It allows you to have a heater without having to maintain it often.

It can be used for both freshwater and marine aquariums. There is a built-in self-limiting positive thermal coefficient (PTC) technology that prevents the water from getting overheated.

Unlike other water heaters, which must be placed horizontally, you need to install this heater in a vertical manner and outside the tank. It is ideal for sump pumps as well as for canister filters.

So, if you don’t have canister filters, then you may wish to opt for other types of heaters.

Inside the filter, it has advanced silk-screened polymer sheets that heat the water. Moreover, if the return tube runs dry for a while, it doesn’t cause any damage to the heater.


  • External heater with PTC technology
  • Suitable for freshwater and marine aquariums
  • Self-switch off to prevent overheating
  • Rotor-dial switch


  • Not water resistant
  • Only suitable for canister filters and sump pumps

Hydor Inline Heater review: Features and Benefits

·      Tube connector

The heater has a built-in clamping system along with a hanging hook, so you don’t need any external clamps for supporting the device.

You can seal the on to the pipe by compression fitting. After you have attached the two ends of the heater into the pipe, you can twist the knobs at both opening ends until you are sure that the heater has been properly latched on.

·      Water flow indicator

The heater is directional; that is, it allows the water to flow only in one direction. The water from the aquarium flows in the filter and then into the heater.

Therefore, to avoid any confusion regarding the manner of installation, there is an indicator on the body of the device indicating the direction of the water flow.

·      Temperature control knob

It has a rotor dial knob by which you can set the temperature higher or lower as per your need. The heater is capable of maintaining a temperature of the range between 65 and 93 degrees.

Once you have set the temperature, it maintains the temperature without any fluctuations. At the maximum, the dial has a swing of 0.1-degree movement.

·      Easy installation and operation

The installation of this gadget is very basic and straightforward. Unlike other water heaters with multiple and complicated control systems and settings, this device has only one manual control.

You can easily switch it on by twisting the rotor dial knob, which is also used to set the temperature of the aquarium. As soon as you switch on the device, there is an audible clicking sound along with an indicator that lights up.

In this way, you can quickly check whether the heater is running or not. The device automatically switches itself off before any incidence of overheating.

·      Lack of noise

Most of the filtration and heating devices tend to be very noisy when they are running. This gadget, on the other hand, is not only convenient to use but is also quite silent during its operation.

·      Easy to maintain

For the device to last long, it needs to be cleaned regularly to prevent any limestone buildup and algae growth inside.

Furthermore, the design of the equipment is straightforward and minimal. Therefore, keeping it clean wouldn’t be a very tedious process. You can easily clean it with a long soft brush.

Final words

Having an external heater helps in de-cluttering your aquarium and gives it a clean look. It allows the fishes to roam freely in the tank.

Also, maintaining a constant temperature is difficult if you have the heater placed at one corner of the tank. However, this model uniformly heats the tank since the water coming in from the filter is heated up and supplied into the aquarium afterward.

We hope our Hydor Inline Heater review can help you make an informed decision.

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