Can I Put My Aquarium Heater Under the Gravel?

Understanding the best placement for your aquarium heater is essential for a safe and adequately warm tank. You might be wondering if you can put your aquarium heater under gravel.

No. Do not put an aquarium heater under gravel because it leads to improperly heated water and puts the heater at risk of being cracked, leading to electrocutions. Instead, install the heater where the manufacturer recommends, based on the model you select.

Keep reading to learn more about why you cannot put an aquarium heater under gravel. This article thoroughly explains the best placement of aquarium heaters and more.

Can I Put My Aquarium Heater Under Gravel?

If you are looking for a convenient location to put your aquarium heater, you might think that under the gravel is a great option. Unfortunately, this is not the case.

It would be best never to put an aquarium heater under gravel unless it is a specially made substrate heater. Do not put the heater under gravel unless you are dealing specifically with a substrate heater. Placing the heater under gravel renders it less effective and a potential safety hazard for you and your fish.

Instead, place your aquarium heater on the back or sides of the aquarium using clips or suction cups. Better yet, follow the instructions with your aquarium heater to place your heater based on the manufacturer’s recommendations correctly.

The Heater Will Be Less Effective

If you were to place an aquarium heater underneath gravel, you are rendering the heater less effective. The layer of gravel essentially traps the heat closer to the bottom of the tank. As a result, the water will be unevenly heated.

This unevenness might not be the biggest deal for fish that aren’t sensitive to temperature. However, many fish are susceptible to temperature, and if the tank is not even and precisely right, they may die.

Since the whole purpose of the heater is to warm the water up to your fish’s ideal temperature, there’s no point in setting it up in such a way that it is not practical.

The Heater Will Be A Safety Hazard

Although an ineffective heater is terrible enough, it gets even worse if the heater gets damaged. Aquarium heaters are designed explicitly with waterproof tubing, often made from glass, and this tubing aims to keep water out of the internal mechanism.

As you might suspect, electricity is used to heat the heater and the aquarium water, and it’s common knowledge that electricity and water do not go well together. Luckily, an effective glass tubing surrounds the heating mechanism so that it can safely heat the water. Without the waterproof casing, your fish would be electrocuted, and you could get electrocuted if you touch the water.

If you were to put gravel on top of the heater, you risk scratching or cracking the glass tubing that keeps everyone safe. Even the most minor cracks can allow in water, electrocuting your cute fishy. Once again, you could get electrocuted in the process.

Because of how dangerous your aquarium can be if the external casing on the heater gets damaged, you should do everything in your power to keep the heater safe and put together. This involves keeping gravel far away from the heater.

Orlushy Submersible Aquarium Heater,150W Adjustable Fish Tahk Heater with 2 Suction Cups Free Thermometer Suitable for Marine Saltwater and FreshwaterOpens in a new tab.

Can An Aquarium Heater Touch Gravel?

You definitely cannot put an aquarium heater underneath the gravel. What about allowing the heater to touch the substrate? Is this just as potentially dangerous?

Unfortunately, it would be best not even to allow your aquarium to touch gravel. Anytime the heater comes in contact with the substrate, even the smallest amount of it, you risk the heater. Position the heater so that it does not come into contact with gravel.

If you place the heater on the back or sides of the aquarium just below the waterline, you will not have to worry about gravel ever touching or damaging your aquarium heater.

How Do Aquarium Heaters Work?

To better understand why you cannot place an aquarium heater under gravel, it’s best to know how these devices work in the first place. Nearly all aquarium heaters today are submersible so that you can place them inside the tank.

Submersible heaters have a thermostat and resistance design to keep a consistent temperature. A capsule of glass protects the internal mechanisms. The thermostat will set off the heating element to heat the water up whenever the water drops below the desired temperature.

Whenever you first turn on the heater, the water column closest to the heater will warm up first. The heat is further distributed to the rest of the tank utilizing conduction and convection. You can speed up this process by correctly placing the heater in your fish tank.

Where Should An Aquarium Heater Be Placed?

Where you place your aquarium heater ultimately depends on the type of heater. Most aquarium heaters have a submersible design. With this design, the heater will go into the water directly. Typically, you can connect them to the back of the tank using clips or suction cups.

Many fishkeepers recommend using two heaters on opposite sides of the tank, resulting in more consistent temperatures throughout the entire enclosure. Smaller tanks might not need two heaters for consistent results.

Orlushy Submersible Aquarium Heater,150W Adjustable Fish Tahk Heater with 2 Suction Cups Free Thermometer Suitable for Marine Saltwater and FreshwaterOpens in a new tab.

Read The Heater’s Instructions

To ensure you know exactly how to set up your aquarium heater, read the instruction manual with your specific heater. The instruction manual will give you more specific ideas about installing the heater based on your product.

One thing to pay special attention to is how far you can submerse the heater. Some heaters can only sit at the top of the tank, whereas others can go further down. Ensure not to submerge the heater further than its recommended depth to work correctly.

Location Is Everything

No matter what kind of aquarium heater you select, make sure that you place it in a safe location. You want the heater to be away from plants, decorations, and other obstacles. Placing the heater too close to obstacles can throw off the temperature and cause your fish to get stuck between the two items, resulting in fish sticks.

Likewise, ensure that the heater is far enough above the gravel that the fish doesn’t get stuck. You want to add plenty of space between the bottom of the tank and the heater for the safest aquarium possible.

Be Safe With Your Aquarium Heater

Practice sound safety tips when doing anything with your aquarium heater. For example, make sure to unplug the heater before changing out any water. Only plug the heater back in once it is fully submerged, and you don’t have to deal with it anymore. This reduces the chance of electrocution for both you and the fish.

If you know you have a particularly aggressive fish, consider investing in a heater guard. The heater guard will help to protect your fish from getting burned. If you aren’t sure what personality your fish has, investing in a heater guard won’t hurt.

Can Aquarium Heaters Be Next To Filters?

Most fish keepers recommend placing your aquarium heater next to the aquarium’s filter. Filters use water flow to draw in particles and distribute the water out again. As a result, placing the heater next to the filter allows the heated water to be further distributed by the water flow.

Furthermore, placing an aquarium heater next to your filter helps to minimize any hot spots or temperature fluctuations. Since the hot water is constantly being moved away from the heater, the entire tank will get the heated water.

The excellent news about placing a water heater next to a filter is, you don’t have to worry about the fish getting stuck between the two either. Because the filter pushes water away and creates a current, you don’t have to worry about the fish swimming up and getting stuck accidentally.

Final Thoughts

Once again, never put an aquarium heater under gravel. It makes the heater less effective, and it puts the glass casing at risk of being scratched and cracked. If scratched, both you and the fish could be electrocuted when the water comes into contact with the electricity.

Instead, place your aquarium heater on the back or side of your aquarium. Try to position it centrally so that the water is distributed evenly. For best results, you might even want to place your heater next to a filter so that the hot water is constantly being distributed.

No matter where you place the heater, make sure that you are safe when dealing with the heater. For example, unplug the heater anytime you refute the water or clean out the tank. Not only will this protect you, but it will protect your fish.


My name is Jaap, and I am a passionate shrimp and fish enthusiast. I rediscovered my love for this hobby with my son and want to share our knowledge and tips with you on this aquarium blog. We cover topics such as setting up and maintaining an aquarium, feeding and breeding your shrimp and fish, and creating the perfect environment for them to thrive.

Recent Posts