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Fish Tank Filter Blowing Bubbles: Explained & Fixed

Lindsey Stanton Profile Picture

By Lindsey Stanton

aquarium filter nozzle with bubbles

Yes, nearly all aquariums require filtration units in order to keep the inhabitants of the tank happy and healthy. There is no doubt about this. However, you might have noticed that your filter is all of a sudden blowing a bunch of bubbles which often raises questions and concerns.

So, why is my fish tank filter blowing bubbles? Well, it’s probably due to one of these 6 reasons that we will cover, and most importantly what you need to do to remedy it.

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Is There A Problem With Bubbles?

Many people ask us why their filter is blowing so many air bubbles. They’re worried that those bubbles are inherently bad for the aquarium. Now, generally speaking, bubbles are not really bad for your aquarium.

They are after all just air, oxygen. In fact, they might actually help to aerate and oxygenate your tank. The benefit here is that fish and plants have more oxygen to breathe, and can therefore live comfortably.

However, of course, there is such a thing as too much. Having your filter blowing too many air bubbles can result in a screen of bubbles that obscures your view of the tank’s interior, plus it does not make it easy for fish to see either. Moreover, these bubbles can also create unwanted water flow and water movement which may not be good for the tank. In all reality, these are only minor concerns.

Now, what you need to know is that the bubbles themselves are not really a problem, at least not the main problem. Yet, the bubbles coming from your filter are being caused or created by something, an underlying problem. These problems, the ones that cause the bubbles, are ones that can be more serious for the health of the tank. Let’s move on and talk about this right now.

goldfish in dirty unclean tank
Image Credit: Chaikom, Shutterstock

The 6 Reasons Fish Tank Filters Blow Bubbles

Ok, so now it is time for us to go over why your fish tank filter might be blowing bubbles. These problems are all actually quite straightforward and easy to deal with, so let’s get to it.

If you have an aquarium filter shooting out bubbles, then try these 6 solutions before going down the replacement route.

1. A Dirty Filtration Unit

The first reason why your fish tank filter is blowing bubbles could be due to it being dirty. When there is a lot of protein stuck in the filtration unit, by which we mean uneaten food, plant matter, and fish waste, it can cause those bubbles.

The high protein content in the water causes air to stick together, thus forming bubbles when it comes out of the filtration unit.

The solution here is to simply clean out your filtration unit. Take it apart, clean the media, wash out the tubes, and ensure that there is no solid waste in any of the filtration components.

A dirty filter will often cause bubbles to form, but generally speaking, this issue is pretty easy and straightforward to solve. Here we are not only talking about the media but about tubing and other components as well. Everything needs to be cleaned.

Close up of a hand disassembling a fish tank waterfall filter to clean it
Image Credit: Ladanifer, Shutterstock

2. High Protein Content

Yes, this is related to the point which we made before, but it goes even deeper. The previous point was about a dirty filter and a high protein content within the filter. However, the problem may be larger than this.

What we mean is that your whole aquarium might have too high of a protein content. This is usually not a big problem with freshwater tanks, but it often happens with saltwater tanks.

Once again, that high level of protein in the water will cause air to stick together, ultimately forming this bubbly and foamy mass that comes out of the filter. For this reason, you need to ensure that you clean the tank regularly.

You need to clean the substrate, remove uneaten food, rotting plant matter, and yes, fish waste too. This should take care of the problem. Moreover, many people who have saltwater aquariums use protein skimmers, a device used to remove proteins from the water (we have covered our top 10 skimmers here). This should also go a long way in remedying a bubbling filter.

3. Old Media Or Clogged Media

The next reason why your fish tank filter might be making a lot of bubbles is due to a problem with the media. This is especially true when it comes to mechanical media, such as foam pads and sponges.

This media does get dirty quite easily. Mechanical media is designed to stop solid waste from entering the filter, and of course to remove this solid waste from the tank. However, as this media gets old and used, it can get clogged.

Yes, mechanical media can be cleaned, for the most part. More often than not, the problem here is a lack of maintenance and proper media cleaning. Clogged mechanical media will prevent air and water from passing through in some places, and will thus force the water and air through the parts that are not clogged.

This will cause bubbles. Therefore, the solution here is to ensure that your mechanical media is as clean as it can be. If it is dirty and worn out past the point of cleaning, it is time to replace that mechanical media.

Coral biological filter media
Image Credit: NRien, Shutterstock

4. Bubbles via Splashing

This is usually not the problem, but in rare cases, it may be. If you have a hang-on back filter or any kind of filter which has the water cascading down atop the surface of the water, it can also create this bubbling effect.

If the flow rate of the hang-on back or power filter is too high, the water coming out of it, and dropping into the tank, will force air into the water, thus creating bubbles. This can also be the case if the water level of the tank is too low compared to the height from which the filtered water is coming down.

Therefore, the easy solution here is to turn down the flow rate of the filter so the water does not have as much force when it drops into the tank. Also, you can try raising the level of the water surface in the tank, therefore creating less space between the water surface and where the filtered water is released.

5. Soaps

Once again, this is somewhat uncommon, as most people won’t use soap to clean their filtration units, but hey, it does happen on occasion. If you have used soap to clean out the components of your fish tank filter, you can rest assured that this is the cause of your bubbling filter.

Simply put, don’t use soap to wash out the filter. If you already have done so, you will need to remove the filter from the tank and rinse it out thoroughly until all soap residue is gone.

While this does not happen often, soap, especially certain kinds, can be very dangerous for the health of your fish and plants, so this is important to know.

soap bars stacked together
Image Credit: christiancmccorbeti, Pixabay

6. Broken Filter Components

The final reason your filter might be blowing bubbles is that the filtration unit itself has seen better days. Yes, aquarium filters break and the components can suffer from issues, ones which are related to physical damage, such as impact, or purely due to age, or in other words, wear and tear.

For one, it could be the diaphragm in the air pump which is worn out. This will allow air to bypass the whole system, thus forcing the air bubbles out of the other end of the filter. Moreover, it could be due to a broken or faulty impeller that continuously loses its prime, thus also creating air bubbles and forcing them through the system.

Quite honestly, this is a harder problem to solve. Yes, they do make aquarium filter repair kits so you can potentially repair the broken pump or impeller, but actually recognizing that something is broken, and in which way it is broken, can be very difficult.

Moreover, if you are not skilled with this kind of thing, even with a repair kit, you might not be able to complete effective repairs. There is also the point that sometimes things are just broken past the point of repair. Simply put, it might be time for you to buy a new fish tank filter.

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Is a fish tank filter supposed to bubble?

Generally speaking, no, a well-functioning filter should not be producing an abundance of bubbles in fish tanks.

If there are enough bubbles to cover the surface of the water, then the filter is either not working properly or may be clogged with debris.

However, a small amount of bubbles is perfectly normal, as this happens when water and air are forced through the filtration unit. There should be a moderate amount of bubbles.

My fish tank filter is not bubbling, why?

On the other hand, if your fish tank filter is not bubbling at all, then there may also be some problems with it.

One problem may be that it is severely clogged, and barely any water or air can get through it. There may also be issues with the impeller, the motor, the media, or tubing.

Generally, cleaning the fish tank filter very well should take care of this, and if the problem persists, you may need to get it repaired, or even buy a new one altogether.

fish tank with filter hose
Image Credit: RaKav007, Shutterstock

Are too many bubbles bad for fish?

Yes, if there are too many bubbles in the water, it usually means that the fish tank is over-oxygenated.

It might sound weird, but yes, there is such a thing as too much oxygen in the water. If there is too much oxygen in the water, it may very well lead to what is known as bubble disease.

It’s characterized by bubbles forming on the skin of the fish, especially on the face and around the eyes. While excessive nitrogen levels more commonly cause this, it can also be caused by too many bubbles or oxygen.

Do bubbles oxygenate water?

To a certain extent, yes, bubbles with oxygenate the water. However, keep in mind that oxygen does need to be dissolved in the water for fish to make use of it.

If the oxygen is purely in the form of bubbles, then the amount which dissolves into the water, and actually oxygenates it, is going to be very limited.

goldfish at surface with bubbles
Image Credit: Pixabay

Will my fish die if I turn off the filter?

Yes, most likely your fish will die if you turn off the filter. Now, it’s not like they will die as soon as you turn the filter off, or even the next day, and probably not the next week either.

However, the longer your filter is off, the more ammonia, nitrates, nitrites, and fish waste are going to build up, and this can result in a wide variety of diseases and illnesses.

Eventually, yes, maybe after 2 weeks or maybe after 2 months, without a filter, most fish won’t make it.

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There you have it, folks. If your fish tank filter is blowing bubbles, it could be due to any of the 6 reasons which we listed above. Besides a purely broken filtration unit, most of these issues have pretty simple fixes. However, you do first need to identify the cause of the problem, which is really half the battle.

Featured Image Credit: Lapis2380, Shutterstock

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