Hydor Inline Heater Review - A Top Aquarium Heater of 2020

Hydor inline heater Review

The Hydor inline heater is one of the top aquarium heaters in the market. Whether you make a self-sustaining aquarium, a biotope aquarium, or a generic one, at some point, you’ll feel the necessity for a heater. An aquarium heater helps to achieve and maintain the optimum temperature for your fish to flourish.

This Hydor inline heater review aims to let you know its features, pros, and cons in detail. You’ll get an honest overview of the product & then decide whether you should choose it.

The heater we are talking about is an external type heater. However, there are other types like submersible or semi-submersible. We choose an external type heater to review since there are some benefits of this sort of heater over others.

External heater doesn’t clutter an aquarium with gears inside since it mounts outside, so you don’t need to sacrifice the aesthetic appeal of your aquarium to set up a heater. Moreover, you’ll get a constant temperature and a much better heat distribution with an inline external heater than a stand-alone one.

Hydor Inline Heater Review

Find the right size and power for your tank. There are two models offered by the company. One is 200W (rated for 65 gallons), and the other one is 300W (rated for 80 gallons). Higher wattage indicates a higher heating power.

Always buy a heater for a specified size of the tank. This may assist you in getting optimum heater performance and also a long-lasting service.

If you buy 200 watts (rated for 65 gallons) to heat an 80-gallon tank, it’ll turn on and off more frequently to keep up the water temperature. Also, it’ll take longer to heat the tank & will function with lesser efficiency. This suggests the heater presumably won’t last long.

Each time while turning on and off, the unit makes an audible click sound. Obviously, it’ll make less click noise if it has to turn on and off less frequently. More click sounds are often monotonous if your aquarium is located in a quiet place. Selecting the proper size heater can alleviate this little problem too.

This heater is only useable with a canister filter. If you don’t want to take the extra hassle of modifying your canister filter hose, select the heater in between available sizes, i.e., 1/2 or 5/8 inch, that exactly match with your hose size. Otherwise, you have to opt for modification of the filter hose.

Useful Features of Hydor Inline Heater

Atomatic Shut Off

The manufacturer claims it’s the first of external heaters with advanced PTC (Positive Thermal Coefficient) technology, which will keep you tension free in terms of overheating. This self-limiting heating element also ensures long-lasting service life.

The feature that nearly all fishkeepers like in a heater is the automatic shut off option. Meaning the heater will shut itself automatically when it reaches the set temperature; otherwise, it may spoil up cooking all of your efforts in the aquarium.

The safety also has an automatic shut off when it runs dry. But, for this instance, you need to be a bit cautious. Since it’s glass inside, with any glass that’s heated and if suddenly exposed to cold water temperature, there’s a possibility that it may crack or break. But, you can prevent the snapping with little extra care.

Before circulating water again, give a while to cool down the heater. Afterward, start the water flow, let it for some time, and then activate the heater. In this way, you can extend the lifetime of any glass made electric heater; as you know, electric appliances stay longer if you handle them well.

The glass won’t break in normal use. If it’s not installed properly & utilized in a way for which it’s not designed for. If glass breaks, you’ll see a noticeable water leak.

Hydor inline heater for fish tank review

Usable to Any Canister Filter

A Hydor inline heater is ideal to use with canister filters. 200W comes in two different diameters, 1/2 inch and 5/8 inch, and 300W only has 5/8 inch. So, It easily fits with the filter hose of 5/8 inch and 1/2 inch inside diameter.

But, you may have a filter that doesn’t match with the heater dimensions. You can still use it; if you have a filter hose, which is ribbed or smaller/larger diameter than this heater size, you need to modify the hose to splice into. For this, you’ll need some adapters, clamps, etc. Local hardware stores can help you to do so.

Adjustable Dial

The full range of temperature setting is 62°F – 94°F. you can set whatever temperature you would like for your heater to maintain within this range. The good part is outside of the heater won’t get hot.

It doesn’t instantly heat the water, but quick enough to boost the temperature and most significantly maintains that within the 0.2 ~ 0.5-degree range. Therefore, just set and forget. It’ll keep doing a good job of having your fish healthy.

Indicator Light

There is a red light indicator, red light glowing means the heater is on. If that’s off, it’s at the set temp. Just to let you know, as you can’t guarantee electrical equipment, if the red light is on and water isn’t getting hot enough, it may be a sign of heater burnout.

Conversely, users mentioned it has a long service life. Some are using the same heater for nearly 5-10 years, so you can think of burnout as a rare phenomenon. The maker provides 02 years of warranty; within this period, they will fix it free of cost if your heater gets faulty under normal use. An excellent, responsive customer care service is in place to serve all of your needs.

Pros and Cons


  • Easy to put in and use
  • Precise temperature control
  • Automatic shut off to prevent overheating.
  • Proper heat distribution throughout the tank.
  • Usable in both fresh and marine water.
  • Long-lasting service under regular use.
  • Two years warranty.


  • Some may find the click sounds boring.
  • Not waterproof, can be inoperable if it’s exposed to water.
  • Not useable with filters except canister and sump pump.
  • It is quite a bit expensive.

Inline Heater Working Principle

Unlike other aquarium heaters, inline heaters do not stay inside the aquarium tank. Typically an inline heater and a canister filter is the only possible combination. You’ll have to install the inline heater at the discharge return line of the filter.

While water is returning to the tank, it passes through the heater. The heater heats water to a preset temperature. The tank water gets warmer. A built-in thermostat shuts the heater when the water temperature reaches the preset point.

After a while, the heater starts again when the water temperature drops. And this cycle continues.

How to Install Hydor Inline Heater

Obviously, you don’t want to call a plumber for installing a simple piece of equipment like an aquarium heater. Yes, you don’t need to since installation is straightforward. Get the hose ready and follow the simple instructions below.

The Hydor inline heater is built to be installed in line with external canister filters. You must place it on the return lines coming from canister filters or a sump pump. This will make sure the water entering the heater is freed from dirt and debris.

It is designed in such a way so that it’s not possible to see inside, whether it’s clogged or not. Therefore, to stop it from clogging up quickly, you must always connect in the return line, i.e., the filtered water line. If it’s clogged, you’ll notice a significant drop in water flow, and then try cleaning your inline heater with a pipe cleaner.

The heater is unidirectional, only allowing flow in one way. A flow indicator on the body indicates the direction of the water flow. Confirm the heater is pointing in the same direction as the water flows into the tube.

With the tube hose of the canister filter, you can splice into, ensuring the heater stays in the vertical upright position. It must remain as upright as possible as per the manufacturer’s recommendation.

There is a problem with the horizontal position, although the heater will heat if the water is flowing through it. However, the thermostat temperature controller may malfunction since it can collect tiny air bubbles. Because of that, unless the controller is right-side-up vertically, it’s likely to work inaccurately. 

Although this heater is built to heat the water, you’ll be surprised to know it’s not water-resistant! In contact with water, it may become non-functional, so always make sure you keep the heater far away from water and never immersed therein.

If you think a video demonstration would be helpful, you can watch the video as well.


Does it make any other sound than click sound?

No, it doesn’t make any other noise usually, since there’s no moving part. If you hear any noise, just thoroughly inspect the heater for any loose, broken, or other notable damage.

What's the difference between 300w and 200w?

Yes, there’s just one difference, and that’s the rating, 200 W is meant to heat efficiently 65 gallons, and 300W is for 80 gallons.

Can I use this with a sponge filter?

No, this is only made by aiming to use inline with a canister filter. It isn’t usable with a sponge filter since there’s no water movement. It requires water movement inside; otherwise, air bubbles will accumulate and make the heater inoperable.


You may have heard horror stories about overheating and burning out all the fishes, but this heater works perfectly. If that happens, it can occur with any heater.

Still, if you would like to be extra cautious or want to add more safety backup, we’ll suggest you purchase an additional temperature controller to regulate the heater. If one fails, the other will keep you safe.

If you are confused over getting an inline external heater, just go for it. You won’t be disappointed! Hydor is a reliable brand; it is a bit costly compared to other heaters, but it’s affordable, and you should not skimp on vital equipment like a heater.

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Sujit Modak Aquarium Tales Owner
Sujit Modak

Hello, everyone! Welcome to my aquarium blog. Fishkeeping is my passion, and I started this fascinating hobby back in 2006. Besides my engineering profession, I deeply studied many fishkeeping topics since I started building my home aquarium. I researched effective aquarium filtration and lighting of planted aquariums. I am keeping 20+ species of freshwater and saltwater fish as my aquatic pet collection. I successfully experimented with a complex ecosystem inside the aquarium, biotope aquariums, aquaponics, etc. I would love to share some learnings from my hands-on experience of the last 14 years. Hopefully, my sharing will be somewhat helpful to make your aquarium journey awesome! 

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