Can You Fully Submerge a Fish Tank Heater?

Estimated read time 5 min read

In this article, we’ll answer the question can you fully submerge a fish tank heater, we’ll also explain the differences between an immersed and submerged heater, and when you should use them.

Fish tank heaters are an essential pieced of equipment for aquarium owners, but if you’ve never used a fish tank heater before, you might have several questions.

For instance;

Can You Fully Submerge A Fish Tank Heater In The Water?

Yes and no. There are many different heaters (internal and external) some can and some cannot be submerged in the water. Internal fish tank heaters should at least be submerged enough to cover the heating element. Submersible internal heaters can be fully submerged in the water.

Keep reading to learn more about how to submerge different kinds of internal fish tank heaters.

This article will also cover some frequently asked questions.

Top Rated Fish Tank Heaters


Are All Fish Tank Heaters Waterproof?

Not exactly.

Almost all internal fish tank heaters must be at least somewhat waterproof to actually heat the water in your aquarium and measure the temperature of that water.

However, some internal fish tank heaters are more waterproof than others.

There are a few external types that cannot be submerged at all, such as in-line fish tank heaters.

In our opinion, in-line heaters are not very effective and can sometimes cause electrical issues, so we don’t recommend them.

Internal Fish Tank Heaters and How to Submerge Them

In terms of internal fish tank heaters, there are many different types you can choose from.

Below you’ll find the different types of fish tank heaters that can be at least somewhat submerged in water;

1. Submersible Fish Tank Heaters

As the name implies, a submersible fish tank heater is designed to be fully submerged in water.

Because these heaters can go fully into the water, they are one of the most effective types of heaters.

A submersible fish tank heater should be placed deep in the water at a vertical, angled, or horizontal position.

If the submersible heater has a thermostat inside, it is best to place it horizontally for the most accurate temperature readings.

Avoid putting a submersible heater near the gravel or substrate, as differences in how your substrate conducts heat could cause the heater’s glass to crack.

2. Immersible Fish Tank Heaters

Immersible fish tank heaters are also known as hanging fish tank heaters.

An immersible or hanging heater hangs from the top of the tank. Most people place them at the back of the tank.

A glass tube that contains the heating element will sit in the water from this position. Secure these heaters well to prevent that glass from breaking.

These heaters are the least expensive, and they are also the most commonly used.

Please note that an immersible heater should not be used in a saltwater fish tank, as salt could get into the glass tube and cause problems.

Note: Did you know that if you don’t install your heater properly you can start a fire? To learn more read; Can a Fish Tank Heater Catch on Fire

3. Substrate Fish Tank Heaters

Substrate fish tank heaters are the least commonly used out of all the types of heaters that can be submerged.

These heaters are made up of wire that is kept inside an insulator.

A substrate fish tank heater must be buried in the fish tank’s gravel or substrate. The wire within the insulator acts as the heating element, and the wire warms the gravel, which warms the water.

A substrate heater is only essential if you are setting up a planted tank, as the substrate fish tank heater prevents the roots of the plants from getting too cold.

This is why they are not used as often as the other types of internal fish tank heaters.

Related: When Should You Replace A Fish Tank Heater? and 5 things to look out for.

Video: Keep Your Aquarium Heater Submerged to Avoid Disasters

Final Thoughts

Can Fluval heater fully submerge?

The Fluval M Series heater is designed specifically to be fully submerged in your aquarium water. It has a mirrored finish to help blend the heater into surroundings by reflecting the aquarium’s colors.

Can I submerge my aquarium filter?

Yes, but it depends on the type of heater you are using. Immersible and submersible heaters are designed to be installed in the water. However, other types of heaters are not designed for use in the water. Ensure you know How To Use An Aquarium Heater, which type of heater you are using, and install them properly.

Can you put 2 heaters in a fish tank?

Placing two heaters in a fish tank is a great idea for larger aquariums to keep the temperature stable and consistent. Also, using tow heaters will ensure you always have a backup heater in case one fails.

You can also use two heaters when first setting up an aquarium to help reduce the time it takes for your aquarium water to heat up.

Whether or not you can submerge your fish tank heater in the water depends on what kind of fish tank heater you have.

Immersible heaters can be somewhat submerged, as they are designed to have the heating element in the water.

Submersible fish tank heaters can be fully submerged, and they are the most effective type of internal fish tank heater.

Substrate heaters also need to be submerged and buried, and these are good for fish tanks that also contain plants.

External fish tank heaters should generally be avoided since they are less effective.


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