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. To help you get started with your sponge filter, follow our step-by-step directions.

Diagram of sponge filter configuration

What is a sponge filter?

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

Both novice and experienced fish keepers love sponge filters. They are inexpensive, simple to clean, and easy to break. Because of the constant bubbling, it provides good water circulation and surface agitation, white being gentle enough to avoid sucking up fish fry, shrimp, and other slow-moving creatures. In case of emergency, you can purchase a battery pack backup to work with our USB air pump.

Find out more about the filtration options available in this article on fish tank filters. We also have recommendations on which type of filter you should use.

Are Sponge Filters able to use an Air Stone?

An air stone is a small weighted accessory that diffuses the air from your air pump into smaller bubbles in the water. To reduce the noise from the sponge filter and increase efficiency, we recommend that you add an air stone inside. The air stone produces a steady stream (instead large, intermittent bubbles), that creates constant lift in the sponge filter. It is similar to an escalator that runs continuously (versus an elevator that stops and starts all the time).

How to set up a sponge filter

1. Remove the sponge filter from the foam and the plastic strainer.

1. The bullseye should be removed from the strainer’s top. Place the air stone on the bottom of strainer. A small length of airline tubing can be used to connect the air stone to either the bullseye’s nipple, or the center. The sponge filter can be connected directly to your bullseye, if necessary. 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 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. The air pump should be placed in the tank’s final position. Next, cut the airline tubing (attached with the sponge filter) to the right 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 install it backwards, no air will flow when you turn on the air pump, so just flip it around.)

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 Side of the Sponge?

There could be many reasons this might happen. Check out the following:

– Did the lift tube have to be cut or removed? The suction from a shorter lift tube may not pull bubbles up the center column as well, and some air could escape. Is the sponge filter clogged with air stones? To make it hang straighter, you may need to shorten the tubing attaching the air stone to the bullseye. Is the pressure of the air pump too high? If a bunch of air is forced into the sponge filter, excess bubbles may leak out the sides.

Which sponge filter would you recommend?

Sponge filters can be used as a basic piece of equipment. There aren’t many differences between brands. However, after a decade of using tons of sponge filters, we made our own with all the improvements and features that we’ve always 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 from a coarse foam with 20 ppi and medium porosity. This allows for particulate to be collected easily without clogging too quickly. The sponge’s surface is large enough for shrimp and fish to enjoy. 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 of the sponge filters we sell are hollow inside and tall enough so that you can install an air stone inside for more efficient filtration and quieter bubbles. You can also connect another sponge filter to the top of the lift tube (without its base), to increase your filtration capability. You can customize these sponges in many configurations. All three sizes of sponges (except the nano sponge) are interchangeable. A stacking of sponges is more efficient than running them individually. They can all run on a single line of air pump. If you need to set up an emergency hospital tank, just remove one sponge from the stack. It’s already seeded in beneficial bacteria, which will help quarantined fish.

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. In an old tank of water, squeeze and wring the foam out several times. 4. Reassemble the sponge filter and put it back in the tank. 5. You can wait for the sponge filter to remove any large particles that are floating in the water.

Sponge filters can be very cost-effective and reliable, making them a great choice for budget-minded users. If you haven’t tried one yet, check out our line of sponge filters and let us know what you think!