Sponge Filters: The Easiest Fish Tank Filter Ever

Because sponge filters can be used in fish tanks, fish rooms and breeding tanks, they’re very reliable and easy to use. They are often confusing for beginners, as they can be difficult to understand how they work, set up, and maintain. For step-by–step instructions on how to make your first sponge filter, see our guide.

Diagram of the sponge filter arrangement

What is a Sponge Filter?

The most basic filter needs at least three components. It includes a sponge filter that sits inside the tank and an air pump that sits outside. There is also airline tubing connecting them. The air pump moves air through the tubing and into the sponge filter’s hollow cavities. The sponge walls draw water through bubbles that rise from the sponge’s interior. 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 bubbles constantly, which provides water circulation and surface movement. The sponge is gentle enough that it doesn’t eat fish fry or shrimp. In case of emergency, you can purchase a battery pack backup to work with our USB air pump.

Our article on fish tank filter options and which one to get will provide more details.

Do I Need an Air Stone for Sponge Filters?

An air stone is small, lightweight accessory that helps to diffuse the air from the pump and create smaller bubbles in water. To reduce the noise from the sponge filter and increase efficiency, we recommend that you add an air stone inside. The air stone creates tiny bubbles instead of intermittent, large ones that cause constant lift in sponge filters. It’s similar to an elevator that stops and starts but is constantly running.

How to set up a sponge filtration

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

1. Take the bullseye off the strainer and place the airstone at the bottom. A small length of airline tubing can be used to connect the air stone to either the nipple, or the center of the bullseye. If your sponge filter is very small you can connect the airstone directly to bullseye. 2. Attach the bullseye to the top of your strainer. Then, place the strainer back in the foam and connect it to the sponge filter’s weighted base. 3. Place the lift tube on one end of an airline tubing roll. Then connect the airline tubing with the nipple at the top of your bullseye. Next, snap the lift tube onto your 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 pump outside, then cut the airline tubing roll attached to the sponge filtre to the required length. The sponge filter’s air tubing has been connected to the 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 install it backwards, no air will flow when you turn on the air pump, so just flip it around.)

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. In a matter of seconds, bubbles should start to form from the sponge filter.

Why Do Bubbles Come Out of the Sponge Side?

There are several reasons why this could be happening, so try checking the following:

– Did you reduce or remove the lift tub? A shorter lift tube does not have as much suction pulling bubbles up the center column, so some air may escape. Is the sponge filter clogged with air stones? You might need to shorten your tubing to attach the air stone and bullseye in order to make it stand straighter. Is the pressure of the air pump too high? Extra bubbles could leak out of the sides if too much pressure is applied to the sponge filter.

Which sponge filter would 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. The base and lift tube were designed with a green color to blend with the planted tanks and hide green algae growth. The foam sponge is black to conceal any fish waste or other debris that might get 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 too fast. It is easy for fish and shrimp to use and clean. Because the sponge is coarse, it doesn’t trap air as much, so it can sink and get water flow immediately. (Fine sponges often have problems with floating, which can cause lack of oxygen in your aquarium and potentially loss of life.)

All sponge filters we sell have a hollow interior and are tall enough that an air stone can be installed inside. Also, if you remove the lift tube, you can connect another sponge filter on top (without its base) to increase filtration capacity. These sponges are customizable in multiple configurations. The three sponge sizes can all be combined (except for the nano sponge). The advantage of stacking multiple sponges (versus running them separately) is that they can run off a single air pump line. If you ever have to set up a hospital aquarium, remove one of the sponges from the stack. It has already been seeded with beneficial bacteria for the fish.

How to Clean Sponge Filters

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. To clean the sponge filter, remove the bullseye and strainer from it. 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. In an old tank of water, squeeze and wring the foam out several times. 4. Put the sponge filter back into the tank. 5. You can wait for the sponge filter to remove any large particles that are floating in the water.

Sponge filters are easy to use, budget-friendly, and very reliable compared to other filter types. You can check out our sponge filter line and let us know your opinion!