Aquarium Sponge Filter: The Ultimate Guide

Sponge filters are a long-time favorite of beginner and experienced fish keepers since they’re cheap, easy to clean, and hard to break.

Since they lack dangerous mechanical parts, sponge filters are an excellent choice for aquariums with smaller fish or low water flow preferences.

This most basic of all filters requires at least three components: a sponge filter (which sits inside the tank), an air pump (which sits outside the tank), and airline tubing to connect them.

The pump pushes air through the tubing into the hollow cavity inside the sponge filter.

Bubbles rise from the inside of the sponge, thus drawing water through the sponge walls.

This water suction process mechanically collects debris from the aquarium and gives beneficial bacteria a place to grow.

The constant bubbling provides good water circulation and surface agitation while being gentle enough to avoid sucking up a fish fry, shrimp, and other slow-moving creatures.

Plus, during power outages, the beneficial bacteria on the sponge stays in the oxygenated tank water (which gives it a longer chance of surviving), and you can even purchase a battery pack backup that works with our USB air pump in case of emergencies.

With minimal parts and uncomplicated upkeep, sponge filters are hardy and entirely customizable when adding control valves and air stones into the equation.

A sponge filter can also be used as supplemental filtration in a traditional freshwater community tank.

Though sponge filters do not provide chemical filtration, they are an excellent way to improve the mechanical filtration in your tank and boost biological filtration.

The sponge portion of the filter is a great place to cultivate a colony of beneficial bacteria that will work to maintain the nitrogen cycle in your tank.

Rather than purchasing an expensive new filter incorporating biological filtration or risk endangering your smaller fish, why not save yourself some money by installing an aquarium sponge filter into your tank?

Keep on reading to see which aquarium sponge filter best fits your needs.

Aquarium Sponge Filter
Aquarium Sponge Filter

How Does An Aquarium Sponge Filter Work?

Aquarium sponge filters work to purify your aquarium environment without any dangerous moving components in traditional aquarium filters.

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 the sponge causes water to be filtered through the sponge – catching debris – and pushes only clean water out of the top of the filter.

As water passes through the sponge, it traps debris,  like fish feces, uneaten food, and decaying plants, filtering it from the water.

The filtered water then passes through the lift tube and back into your tank.

While this filtration method may seem basic, it’s pretty effective!

Since sponge filters don’t have a way to force water through them, they are used in conjunction with an air pump, air stone, or powerhead.

Sponge filters are useless without some form of an air pump or a similar device.

While they used to be the preferred way to filter an aquarium, advancements in filter technology have made the sponge filter less popular.

But sponge filters are still handy for your tank!

While sponges continue to make a tremendously cheap primary filter, they are also often used to add an extra layer of protection to your tank.

When used this way, sponge filters are sometimes referred to as pre-filter sponges because they are precisely that – a sponge that sits on your filter tube intake.

If you were wondering, you could also use a sponge filter with your primary filter to prevent it from clogging, removing an extra layer of aquarium debris before any water reaches your primary filter.

Depending on your setup, a sponge filter could be the perfect addition to your aquarium!

When Are Aquarium Sponge Filters A Good Choice?

Sponge filters are excellent when safe and gentle filtration is needed, such as in a fry tank where young fish could be sucked into the intake of standard filters.

 Fish species such as bettas that do not thrive in strong currents also benefit from sponge filters.

Shrimp are another species that requires very gentle filtration rather than a vital intake that would suck them in.

Sponge filters are also great for hospital tanks, where fish are often weak and cannot tolerate the more potent suction from a standard filter inlet.

Sponge Filters for a New Aquarium

Another use for sponge filters is to jump-start a new aquarium.

A sponge filter can be run on a well-established aquarium for several weeks or months to establish biological colonies.

Once the new aquarium is set up, the matured sponge can be placed in a bag of water and transferred directly to the new tank, thus maintaining the biologicals.

This gives the new tank an immediate biological boost, which benefits the fish in the new aquarium by reducing the ammonia and nitrite spikes experienced in a new tank.

Some aquarium owners keep a small sponge filter running in one or more of their main tanks, so they are prepared to set up a new aquarium or an emergency tank.

Pre-Filter Use

Sponge filters work exceptionally well as a pre-filter on the inlet of a canister filter.

The sponge filters out more extensive, significant pieces of debris in your tank, which helps keep your canister from clogging down the road. 

Additional biological filtration is also provided this way, and the sponge is ready for use in setting up an emergency aquarium should the need arise.

Remember that multiple sponges may be used with sponge filters, an air pump, a powerhead, a canister, or another filter.

This provides additional biological and mechanical filtering ability and allows maintenance staggered, so not all sponges are disturbed simultaneously.

It also gives the owner an extra sponge or two to seed a new tank with, if desired.

Aquarium Sponge Filter
Aquarium Sponge Filter

How Do I Set Up An Aquarium Sponge Filter?

Setting up an aquarium sponge filter is easy; all you have to do is follow these steps:

Take apart the sponge filter and remove the plastic strainer from the inside of the foam.

Remove the bullseye from the top of the filter and put the air stone at the bottom of the filter.

Connect the air stone to the nipple or center of the bullseye using a small length of airline tubing.

If the sponge filter is tiny, you can simply connect the air stone directly to the bullseye.

Snap the bullseye onto the top of the filter, put the filter back inside the foam, and then connect the strainer to the weighted base of the sponge filter.

Slip the lift tube over one end of the airline tubing roll and connect the airline tubing to the nipple on the top of the bullseye.

Then, snap the lift tube onto the bullseye.

Place the sponge filter into the aquarium and squeeze out any bubbles from the foam if it’s floating.

Place the air pump in its final location outside the tank, and then cut the airline tubing roll (attached to the sponge filter) to the proper length so that it’s long enough to reach the air pump.

Connect the newly cut air tubing from the sponge filter to the air pump. If the air pump is located below the top of the aquarium, you need to add a check valve to prevent water from flowing into the airline tubing whenever the air pump is turned off, or the power is out.

Cut the airline tubing (between the sponge filter and air pump) a few inches outside of the aquarium, and then attach the check valve in between so that the end of the check valve with the flapper (looks like a colored or horizontal bar usually) is facing the air pump. If you install it backward, no air will flow when you turn on the air pump, in which case all you need to do is flip it around.

Connecting The Air Pump

If you are struggling to connect the air pump to your sponge filter successfully, we’ve created a quick walkthrough to ensure your filter is running smoothly.

To connect your air pump to your sponge filter:

1. Create a drip loop with the power cable of the air pump (to ensure moisture will not make contact with the plug), and then plug in the air pump.

2. You should see bubbles coming from your sponge filter within a few seconds.

If you are still having difficulty connecting your air pump, numerous guides on Youtube and Google can help.

Thankfully, the community of aquarium-lovers only grows by the day, and so do the available care resources.

What Is A DIY Aquarium Sponge Filter, And How Can I Make One?

A DIY Aquarium Sponge Filter is exactly what it sounds like; an aquarium sponge filter made entirely from items around your home.

While there are many more in-depth guides for DIY sponge filters, this walkthrough will help you make a fully-functional basic sponge filter for your aquarium.

Here’s what you’ll need to get started:

  •    Filter sponge
  •    Sharp knife
  •    Hard plastic tubing
  •    Hammer
  •    One small nail
  •    Styrofoam
  •    Air pump
  •    Aquarium airline tubing

First, cut a piece of filter sponge to the desired shape and size using a sharp knife. For corner placement, the ideal shape form for the sponge is a triangle.

 To cut your filter sponge into a triangle, cut a square in half diagonally from one corner to the opposite corner.

 A circular, square, or rectangular shape is sufficient for other placements within the tank.

Make holes in the piece of rigid plastic tubing by driving a small nail through both sides of the tube with a hammer.

 First, measure the tube against the height of the piece of filter sponge you cut to determine how much of the line will be inside the sponge.

Mark the sponge height on the tube and make approximately 8 to 10 holes per inch of tubing inside the sponge.

Plug the end of the hard plastic tube with a piece of Styrofoam and insert it into the center of the sponge by first making a depression in the sponge with your finger, then pressing the line into the hole through the sponge.

Attach the intake valve of the air pump to the top of the hard plastic tube.

Cut a piece of aquarium airline tubing to a length of 3 to 4 inches and attach it to the outtake valve of the air pump.

Place your sponge filter in the desired location in your aquarium.

Secure the air pump to the wall of the aquarium with suction cups, if desired, and position the output tube so that water is released near the surface.

Some tanks require a filtration system to keep the fish within safe.

Powerheads and canister filters have too much suction power to be used in fry and hospital tanks, and undergravel filters do not provide the necessary aeration.

 If you need a simple filtration system for one of these tanks but do not want to spend much money, consider building your sponge filter system with an air pump.

By using some of the materials you already have, you can create a customized filtration system that will not harm newly hatched fry or sick fish.

How Do I Clean My Sponge Filter?

While a sponge filter helps to clean your aquarium, it’s essentially like a trash can that collects waste in your aquarium.

This also means it needs to be emptied every once in a while.

We recommend cleaning your sponge filter once a month or whenever you see a decrease in bubbles (caused by the foam getting clogged up with detritus).

When taking the sponge filter apart, disconnect the bullseye from the strainer (take off the whole top part of the filter), so you can easily remove the foam part for cleaning.

Use a plastic bag to scoop the foam out of the water so the residue won’t spread and make a big mess in the aquarium.

Squeeze and wring out the foam several times in old tank water.

Reassemble the sponge filter and put it back in the tank.

If many particles are floating in the water, wait an hour or so for the sponge filter to clean it up.

Sponge filters are easy to use, budget-friendly, and reliable compared to other filter types.

Do a deep clean once a month to ensure your sponge filter works 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 two weeks should be sufficient.

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