How Does A Sponge Filter Work? Setup Guide, Cleaning Tips, & More

    How does a sponge filter work

    When it comes to choosing a filter for your aquarium, there are quite a few options on the market. In this post, we will be focusing on the sponge filter and asking; how does a sponge filter work?

    These super-simple filters work using just an air pump, sponge, and airline tubing. 

    A sponge filter works through an airline hose that transfers air from the pump, into the tubes of the filter. The air passing into the hollow inside of the sponge causes water to be filtered through the sponge – catching debris – and pushes only clean water out of the top of the filter. 

    By sucking the water through a sponge, this automatically filters out any dirt and debris and also provides a place for controlled growth of good bacteria and tank-friendly organisms.

    Now let’s take a closer look at sponge aquarium filters and find out why they could be a great choice for your fish tank.

    What Is A Sponge Filter (For An Aquarium)?

    A sponge filter is a beginner-friendly form of aquarium filtration system to help keep the water clear, cleaner and provide a steady current in your tank.

    With minimal parts and uncomplicated upkeep, sponge filters are hardy and quite customizable when it comes to adding control valves and air stones into the equation. Keep reading to see which configuration suits your aquarium needs the best.

    Types of Sponge Filter

    You can find these filters in both single and double sponge formats – both of which have their merits. 

    Single sponge tank filters are ideal for smaller setups where space may be limited. However, some models are suitable for aquariums of up to 25 gallons.

    Suppose you’re worried about the aesthetics of a sponge filter. In that case, you could opt for a corner filter that has a 90-degree angle, triangle shape, and would slot neatly into the back corner without detracting from your beautiful aquascaped tank. 

    Double sponge filters can be used for almost all tank capacities, depending on their size. 

    Small twin filters will cover up to 10 gallons, and large twin filters up to 55 gallons. They are often made with suckers fixed to the back so they can be attached to the side of the tank, as far above the substrate as you like.

    Having two filter sponges means you could set up a new tank much quicker by replacing one sponge with a new one and using the old to start a quarantine or breeding tank, for example.

    Sponge Filters with Air Stones

    You may have also seen sponge filters with air stones or ceramic bio filter media. They might look a little fancier, but more often than not, they aren’t necessary.

    Air stones can be purchased separately and added to certain models of filter using extra airline tubing. They will help to break down the air into smaller bubbles and reduce any noises that the sponge filter may create. 

    How Sponge Filters Clean Aquarium Water

    How does a sponge filter work?

    The way sponge filters clean aquarium water is by trapping debris from the water and filtering clean water back into the tank.

    Air is pumped through airline tubing and into the filter, filling the hollow space down the middle of the sponge and causing bubbles to form. These bubbles assist the sponge in drawing up water, pulling it into the tube and up out of the top of the filter.

    The tiny air bubbles formed also help to increase oxygen solubility.

    As the sponge pulls water through its porous surface, it traps debris, leaving the water clean as it is passed out of the filter at the top. Since debris is being trapped within the sponge, it leaves the water clear and clean. 

    It’s actually a really simple and cheap way to keep your aquarium water free from nasties.

    Also, any aquarium-friendly organisms and helpful bacteria can then live and grow on the sponge. 

    These important good bacteria convert ammonia to nitrite and nitrite to nitrate, further cleaning your aquarium water. Check out our post on how to change aquarium filters without losing bacteria.

    How To Setup Your Sponge Filter

    It could not be easier to set up a filter for your aquarium than using one of the sponge varieties!

    Things you’ll need before setting up your filter will be:

    • A sponge filter (see our list of sponge filters in the “best sponge filters” section)
    • An air pump (check this is powerful enough to suit the size of your tank)
    • Airline tubing (check this is the correct size for your model of filter)
    • Airflow valve (optional – to control how much air is pumped through the filter)

    Once you have all of these at hand, follow these steps:

    1) Assemble your sponge filter (if it does not arrive assembled)

    • Single sponge filters should have a weighted base with a detachable extender (that keeps the sponge from touching the substrate).
    • On top of this will be a plastic tube with holes down the sides, which slots inside the sponge. There may be two parts for this, depending on the brand of filter you have.
    • An extra piece may be fitted to the top, onto which the airline tube can be slotted.
    • The filter may also have an uplift tube to increase water flow. This is optional or can be trimmed to suit the depth of your fish tank.

    2) Attach one end of the airline hose onto the filter – there will be a small extrusion onto which the correct sized tubing will fit perfectly.

    3) Attach the other end to the air pump.

    4) If you have a stopper valve or airflow valve, make sure to fit these into the tubing between the pump and filter with the airflow valve on the side closest to the pump.

    5) As you add the filter into your tank, you may find that squeezing it will help it soak up water and sink more easily – even though bases are weighted, your filter may float for a while.

    6) Once the filter is in place, turn on the air pump at the mains and adjust airflow as needed.

    QUICK TIP: Store your air pump above the tank if possible; this will stop any water from flowing back into the pump during a power outage. Investing in a stopper valve is another option to keep things safe.

    Aquarium Sponge Filter Benefits

    There are so many benefits to sponge filters for your aquarium, so let’s take a look at those now:

    • Cheap to buy – you can purchase these filters in multipacks to get an even better deal!
    • Beginner-friendly – sponge filters are so simple to use; they’re great for those just starting out in the world of fish keeping.
    • Efficient – due to the way sponge filters work, debris is collected from the water by the sponge, creating a place for good bacteria to convert ammonia into nitrates.
    • Adaptable – easy to control airflow to suit a huge variety of tank sizes and bioload situations. Air stones can be added to help reduce bubble size and noise.
    • Easy to obtain – you can find a huge selection of sponge filters online and at pet stores. (Check out some of our favorites from Amazon below.) Extra parts are also readily available.
    • Great for a vast range of fish types.
    • Robust – these simplistic aquarium filters are pretty hard to break, as they’re only made up of a few parts.

    How To Clean An Aquarium Sponge Filter

    How to set up a sponge filter
    Boesemani rainbowfish (Melanotaenia boesemani)

    1) Use a ziplock bag – big enough to fit the sponge filter inside – to remove the sponge from the water gently.

    • Fill the bag with water from the tank to help it sink to the bottom.
    • Pick up the filter carefully, trying not to disturb the dirt in the sponge.

    2) Once the filter is safely in the bag, remove the airline tube and leave it in the tank safely.

    3) Take the bag over to a bucket, take out the filter’s plastic center, and start squeezing the sponge inside the bag. This will make the water fill with fish waste. You may want to wear gloves!

    4) You may find that the plastic center needs emptying and cleaning too.

    5) Take out the sponge from the bag and tip out the gross water into the bucket.

    6) Squeeze the sponge against the sides of the bucket to remove even more gunk before replacing it into the ziplock and filling it up with water from the tank again.

    7) Repeat this process until the bag water no longer looks brown and disgusting.

    8) Once you’re satisfied with the cleanliness of the sponge, put the filter back together and replace it in the aquarium.

    It’s not the nicest of jobs, but if you want a nice clean fish tank, you’ll want to make sure to clean your sponges as soon as you notice them looking a little clogged up. Just ensure you’re cleaning them in the correct way.

    Best Sponge Filters

    Finding a sponge filter for a fish tank is not a difficult task; just check out our selection below of a few different types of sponge aquarium filters:


    Why are bubbles coming out of the side of the sponge?

    You could have bubbles coming out of the side of the sponge because you may have a shorter lift tube, so not as many bubbles are being pulled upwards. This causes bubbles to escape through the sponge.

    Another reason could be that your air stone has fallen off or isn’t sitting right inside the filter.

    Check the air pressure to make sure it’s not too strong, as this could be causing a surplus of air which can only escape through the sponge.

    How often should you clean an aquarium sponge filter?

    Do a deep clean once a month to ensure your sponge filter is working properly. If you notice it looks a bit clogged with detritus or there is a reduction in bubbles, it could be time to clean.

    Some fish breeds produce more waste than others, so you may find that once a month is too long to wait. In this case, every 2 weeks should be sufficient.

    How often does a sponge filter in an aquarium need to be changed?

    It is recommended that filter sponges be changed every 6 months, but if you clean them carefully and regularly, sponges could be reused until they stop doing their job, start to break or rip.

    How long does it take to cycle a new aquarium with a sponge filter?

    New aquariums could take between 4-6 weeks to cycle and grow the necessary beneficial bacteria needed to break down ammonia. 

    If you have an existing aquarium with more than one sponge filter, you could take one from your old tank and put it into the new tank. This should speed up the setup.


    After looking more closely at how a sponge filter works, we’ve learned that they’re a really great option for many an aquarist – newbies and seasoned pros alike!

    A sponge filter uses a straightforward vacuum technique to draw water from the tank and capture poop and debris in the process. This leaves your tank looking crystal clear and creates a great environment to convert nasty ammonia into nitrates.

    These easy to obtain, cheap to buy, simple setup filters might be just what your fish tank needs. 

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