Sponge Filters: The Easiest Fish Tank Filter Ever

Because they’re reliable and simple to use sponge filters are very popular in fish stores, fish room, and breeding tanks. But beginners often have many questions on how they work, how to set one up, and how to keep them clean. For step-by–step instructions on how to make your first sponge filter, see our guide.

Diagram of sponge filter configuration

What is a sponge filter?

The most basic filter requires at least three components. A sponge filter, which sits inside the tank, an air pump (which is outside the tank), as well as airline tubing to link them. The air pump pushes air through the tubing into the hollow cavity inside the sponge filter. The sponge walls are drained by bubbles rising from the sponge. This water suction process mechanically collects debris from the aquarium and gives beneficial bacteria place to grow.

Because they are simple and inexpensive, sponge filters are a favorite among both novice and veteran fish keepers. It provides water circulation and surface agitation through constant bubbling. White is gentle enough to not eat shrimp or fish fry. You can also purchase a backup battery pack that will work with our USB pump to keep your sponge alive during power outages.

You can find more information about filtration options in our article Fish tank filters. Which one should you get?

Do I Need an Air Stone for Sponge Filters?

An air stone is a small weighted accessory that diffuses the air from your air pump into smaller bubbles in the water. An air stone can be added to the sponge filter’s interior to reduce bubbling and improve filtration efficiency. The airstone creates small bubbles that are steady and continuous, rather than intermittent large bubbles that move in a slow fashion. This gives the sponge filter constant lift.

How to Set Up a Sponge Filter

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

1. Remove the bullseye from the top of the strainer, and put the air stone at the bottom of the strainer. Connect the air stone to the nipple or center of the bullseye using a small length of airline tubing. You can connect the sponge filter directly to the bullseye if it is small. 2. Place the bullseye on the top of the strainer and then attach the strainer to its weighted base. 3. 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. 4. Place the sponge filter into the aquarium and squeeze out any bubbles from the foam if it’s floating. 5. Place the air compressor in its final place outside the tank. Then, cut the airline tube roll (attached at the sponge filter), to the correct length. Connect the newly cut air tubing from the sponge filter to the air pump. 6. 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 place it backwards, it will not flow air when you turn on your air pump. Instead, flip it over.

1. Make a drip-loop with the power cable to the air pump. This will prevent moisture from coming in contact with the plug. Finally, plug the air pump into the outlet. After a few seconds you will see bubbles from the sponge filter.

Why are bubbles coming out of the Sponge’s side?

This could be due to many reasons, so check the following:

– Did you shorten or remove the lift tube? A shorter lift tube does not have as much suction pulling bubbles up the center column, so some air may escape. – Is there a crooked air stone in the sponge filter? To make it hang straighter, you may need to shorten the tubing attaching the air stone to the bullseye. – Is the air pressure from the air pump too strong? Excessive bubbles can leak from the sides of the sponge filter if too much air is forced into it.

Which Sponge Filter Do You Recommend?

Sponge filters can be used as a basic piece of equipment. There aren’t many differences between brands. After a decade of trying out many sponge filters, we finally made our own. We added all the features and improvements that we wanted. We designed the base and lift tube with a green color to blend in with planted tanks and easily hide green algae growth, whereas the foam sponge is black to best conceal fish waste and detritus that gets sucked in.

The sponge is made of a coarse foam at 20 ppi with medium porosity. It can easily collect particulate and prevents it from clogging up. It is easy for fish and shrimp to use and easy to clean. Plus, the coarse sponge doesn’t trap as much air, allowing it to get nice water flow and sink immediately. (Fine sponges often have problems with floating, which can cause lack of oxygen in your aquarium and potentially loss of life.)

Our sponge filters are hollow inside. They can be stacked high enough to accommodate an air stone. Also, if you remove the lift tube, you can connect another sponge filter on top (without its base) to increase filtration capacity. You can customize these sponges in many configurations. All three sizes of sponges (except the nano sponge) are interchangeable. Stacking multiple sponges, rather than running them separately, has the advantage that they can be run off one air pump line. You can also remove one sponge from the stack to create a hospital tank. The sponges are already seeded and ready to go for quarantine.

How to Clean a Sponge Filter

Yes, a sponge filter helps to clean your aquarium, but it’s essentially like a trash can that collects waste and needs to be emptied out every once in a while. We recommend cleaning your sponge filter once a month or whenever you see a decrease in bubbles (which is caused by the foam getting clogged up with detritus).

1. When taking the sponge filter apart, disconnect the bullseye from the strainer (i.e., take off the whole top part of the filter) so you can easily remove the foam part for cleaning. 2. Use a plastic bag to scoop the foam out of the water so that the detritus won’t spread and make a big mess in the aquarium. 3. Squeeze and wring out the foam several times in old tank water. 4. Now, assemble the sponge filter and place it back in your tank. 5. You can wait for the sponge filter to remove any large particles that are floating in the water.

Sponge filter are simple to use, cost-friendly, and more reliable than other types of filters. Check out our selection of sponge filters to see if you’ve tried one. Let us know your thoughts!