Why Your Fish Tank Heater Suction Cups Won’t Stick Or Stay On & How You Can Rejuvenate Them.

Estimated read time 7 min read

In this article, we’ll help you understand why your fish tank heater won’t stick, how to make them stick better, and even how you can rejuvenate them.

You would think a fish tank heater that comes with a suction cup would be a helpful thing.

Well, guess what?

They don’t always stick to the aquarium the way they should.

And when they don’t stick, what should you do? Why won’t the suction cups stay on?

A fish tank heater won’t stick if the suction cups or the aquarium’s glass is too dirty. The suction cups could also be too old or made of a flimsy material. Clean the cups and the glass first. If that fails, there are other things you can try. 

Let’s get into it;

Related: How to use a fish tank heater


Our Top Recommended Suction Cups For Fish Tank Heaters

How Do You Get Suction Cups To Stick In A Fish Tank?

The best way to get suction cups to stick is by placing them on the glass when the aquarium is dry.

When you apply a suction cup in a full aquarium, water that comes into contact with the inside of the cup can cause air bubbles, which prevents the suction cups from creating a strong seal.

Another thing you can do is press on the very center of each suction cup while pressing on the other side of the glass with your opposite hand.

Doing this makes it more likely that you will get all of the air out from between the suction cups and the glass, preventing the cups from sticking.

To understand this a bit better, let’s look at a few reasons why they don’t stick.

Reasons Why Your Aquarium Heater’s Suction Cups Won’t Stay On

The following are the most common reasons why your fish tank heater won’t stick or stay on;


Some suction cups are made of a material that is too stiff to work very well.

Because the plastic that some suction cups are made is too stiff it can let air in too easily, which keeps the cups from applying pressure and sticking to the aquarium glass properly.


Even if they are made of good material, old suction cups often become worn out.

At 42 years old, I know how that feels. ?

As they age, the outer edges are no longer airtight as the cups start to wear, which leads to the same issue as having poorly made suction cups.


Sometimes, users neglect to apply the suction cups properly.

If the glass or the suction cups have any moisture or air between them, the cups will not be handy.

See the next section for more information about applying suction cups correctly.

Dirt & Algae

Dirt and algae that gets between the suction cups and the glass is another thing that keeps the suction cups from creating an airtight seal.

While algae is typically easy to see and remove, dirt is sometimes invisible to the naked eye.

Now that you know some reasons they won’t stick, how do you get them to adhere correctly and last?

What Makes Them Stick Better? Applying Them The Right Way

Here are a few things you can do to make your fish tank heater suction cups stick better:

Don’t Move Them (Ever)

While it may be tempting to readjust the suction cups constantly, you should do your best not to move them once you have them stuck to the glass.

Frequent movement is likely to introduce air between the cups and the glass and make it harder for them to stick.

Clean the Glass

Cleaning the aquarium glass before applying the suction cups is an excellent way to eliminate debris or any lingering algae that might interfere with the cups.

If the glass is clean, there is a much better chance that the suction cups can work by directly contacting the surface.

Clean the Suction Cups

Cleaning the suction cups is also essential, as they are most likely dirty from attempting to stick to dirty glass.

You can wash the suction cups out with a scrubby and a little bit of warm water.

Do not leave the cups damp, but a small amount of moisture will help the suction cups stay in place by forming a tighter seal on the glass.

Apply Suction Cups To Dry & Clean Glass

Again, placing the fish tank heater in when it is already full of water will keep the suction cups from making proper contact with the glass.

So it’s best to apply the suction cups while the tank is dry and after you have cleaned the glass.

Allow the glass to dry after emptying or cleaning the aquarium.

How Do You Restore & Rejuvenate Suction Cups?

Although this method probably will not work for suction cups that are old and have worn-out edges, many users have been able to restore suction cups by doing the following:

Boiling Them in Water

Boiling suction cups in hot water will often restore their pliability and make it so the cups can form a proper seal once more.

You can boil them in a pot on the stove or even drop them in a mug of water and microwave them for about two minutes to get similar results.

After this, let them cool and follow the above recommendations to get the best seal.

Related: When should you replace a fish tank heater

Aquarium Suction Cup Alternatives For Your Aquarium Heater

In the end, if you’ve had enough of dealing with sections cups that don’t’ stick, there is an alternative you can try out.

The following product is one of the best alternatives available:

Best Magnetic Aquarium Heater Holder

ZooMed MagClip Magnetic Suction Cups

These are some of the best options to hold your fish tank heater or other equipment in place.

Unlike rubber suction cups, these industrial-strength magnets cling to one another through the glass and hold the heater in place.

They come with six clips of various sizes to fit any heater.

Last Resort: Buy New Aquarium Heater Suction Cups

There are some excellent rubber suction cups out there for fish tank heaters if you are not ready to give up on them just yet.

Pawfly Aquarium Heater Suction Cups

These are made of a smooth plastic that forms a very effective, airtight seal.

These suction cups fit most standard size aquarium heaters and maintain their grip for months at a time, even in hard water that causes a lot of mineral build-up.

Key Takeaways

Every piece of equipment you use in your aquarium will get old and need to be replaced.

However, if you take care of your suction cups by applying them the right way and keeping them clean, they should last a long time.

Lastly, if you don’t want to use a product that will eventually run its course, maybe it’s time to try something new, like a magnetic suction cup.

Tank on. ?


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