How to Place a Heater in an Aquarium—Where Do You Put it

How to Place a Heater in an Aquarium—Where Do You Put it

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If you plan on keeping tropical freshwater fish in your aquarium, you will need to heat the water to mimic the temperature of your fish’s wild environment.

But exactly how are you supposed to place the heater in the fish tank to get the most value from it!

Well, the short and quick answer is…place the heater to the back or side of your fish tank using suction cups, making sure it is near the maximum water flow for even heat distribution.

Preferably, place it near the filter outlet or inlet, in the stream of a powerhead, or next to an air pump where the water flows directly past the heater.

You can also choose to position the heater either horizontally or vertically in the tank, but make sure it does not touch the walls or substrate (more so a thin layer of gravel) because the heat difference will likely crack your heater glass.

Read on for more tips on positioning a heater inside a fish tank.

How Do Aquarium Heaters Work

To best understand how and where to place a heater inside your fish tank, it is important that you first know how internal (submersible) fish tank heaters work.

Submersible heaters are most times a resistance with a thermostat introduced into a capsule of glass and designed to increase the water temperature of an aquariums.

In simpler terms, it is a glass tube with a heating element wound around a ceramic or glass insert. The thermostat turns the heating element on to maintain the required temperature.

Once you turn on the heater inside the tank, it warms up the water column closest to it first, then the heat is distributed throughout the tank by conduction and convection.

The process is optimized by placing the heater in the right position and angle inside the aquarium.

Where Do You Put a Heater in a Fish Tank

As I stated above, the efficiency of your aquarium heater depends a lot on where and how you place it inside your fish tank.

All submersible heaters go inside the aquarium, as we have already established. Usually, fish keepers like to clip them at the back of the tank using suction cups in a space with plenty of water current and little to no obstacles such as plants and decorations.

Internal heaters can also be placed fairly-low in the water and even on the sidewalls of an aquarium, though in that position the unit won’t be central as you would want it to be, meaning the heat won’t spread evenly.

So, I recommend putting your aquarium heaters on the sidewalls or in corners when using two units in the same tank, which is quite common and advisable.

That said, regardless of how low you put the heater in your tank, it’s essential to keep it off the gravel as the difference in heat conductivity between the water and substrate could result in the heater glass cracking.

Finally, make sure you provide enough space between the heater and gravel or the side of the tank to keep your fish from getting stuck against the heater and get burned.

Can You Place Your Aquarium Heater Next to a Filter

Yes, you can place your aquarium heater next to a filter. I actually recommend it especially if the heater on the filter’s maximum water flow, such as the near the outlet or inlet.

Positioning your aquarium heater next to the water flow results in the adequate circulation of heat, which boost the conduction and convection process and warms your aquarium evenly.

Placing your heater next to a filter inlet or outlet or with a bubbler under it also ensures the current carries the heat away from the heater preventing having a hot spot, which usually makes heaters turn off prematurely.

Moreover, you won’t have as many problems with heaters or temperature fluctuation doing it this way.

How to Position Your Aquarium Filter

Most aquarium filters are meant to be placed at a 45-degree angle, but it does depend on the one you have. Also, most aquarists place them in the middle of the back wall, but with more than one filter, you can place each on either side of the tank, even in corners

However, putting your heater at an angle and on the sides might mess with your aquarium aesthetics.

Also, placing a heater at an angle was (is) more important when using an air-driven filtration because they do not create enough current, but with power filter, it’s not so important. As long as there is good flow around the heater, your fish tank should warm up evenly.

Can You Place an Aquarium Heater Vertically or Horizontally

Submersible aquarium heater can be installed horizontally near the bottom of the tank or even vertically. Arguably, setting your aquarium heater in a horizontal position is the more effective way because heat rises and disperse better.

Place your aquarium heater towards the back of the aquarium horizontally and just a few inches above your substrate. This way the heat will rise and disperse better.

Also, you don’t always have to turn your heater off when doing water changes if you place it horizontally because it will mostly be below the waterline.

Should you opt to put the heater vertically, consider hiding it behind plants or decoration the keep your aquarium aesthetics intact.

With all that said, you might not notice a big difference in the way your tank heats up regardless of how you place your heater. Therefore, your choice might mostly be a preference depending on how the heater looks in your fish tank.

5 Aquarium Heater Tips Every Fish Keeper Should Have

Beyond the where and how of placing your heater in the tank, here are five more tips on the same topic.

  1. Always unplug your heater before carrying out any water change then plug it back when the heater is fully submersed.
  2. Let the heater cool for at least 30 minutes before removing it from the aquarium, and after returning your heater in the tank, wait at least 30 minutes before plugging it back in.
  3. Use a thermometer to check the temperature of new water in the same across your aquarium. You don’t want a hot spot inside your aquarium.
  4. Use an aquarium heater guard to protect it from boisterous fish and to keep your fish and plant debris. A heater guard will also keep your heater from burning your fish.

Happy fish keeping Remember to follow us on Facebook and Instagram for more insight, hacks, and tips

Eddie Waithaka

Resident Content Creator and Marketer at AquariaWise who talks about aquariums and fish and aquascapes a lot.

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