Sponge Filters: The Easiest Fish Tank Filter Ever

Because sponge filters are so reliable and simple to use, they are a popular filter in fish shops, fish rooms, breeding tanks, and fish houses. Many people are unsure how sponge filters work and how to clean them. To help you get started with your sponge filter, follow our step-by-step directions.

Diagram for sponge filter setup

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.

Sponge filters are a long-time favorite of both beginner and veteran fish keepers since they’re cheap, easy to clean, and hard to break since they have very few mechanical parts. The constant bubbling provides water circulation, surface agitation and good water circulation. It is gentle enough not to eat fish fry, shrimps, or other slow-moving animals. 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.

Do I Need an Air Stone for Sponge Filters?

An airstone is a small accessory that weighs down the airflow from your pump to create 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 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. You can remove the sponge filter by removing the plastic strainer.

1. Take the bullseye off the strainer and place the airstone at the bottom. Connect the air stone to the nipple or center of the bullseye using a small length of airline tubing. If the sponge filter is very small, you can simply connect the air stone directly to the bullseye. 2. Snap the bullseye onto the top of the strainer, put the strainer back inside the foam, and then connect the strainer to the weighted base of the sponge filter. 3. The lift tube should be placed over the end of the roll of airline tubing. Connect the cable to the nipple at the top of your 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. It is best to flip the check valve around so that air doesn’t flow if it is installed backwards.

1. To prevent moisture from getting into the plug, create a drip loop using the power cable. Then plug the pump in. Within a few seconds, you should see bubbles coming from your sponge filter.

Why Are Bubbles Coming out of the Side of the Sponge?

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

– Did the lift tube have to be cut or removed? Because a shorter lift tube doesn’t have as much suction pulling bubbles upwards the center column, some air can escape. Is the sponge filter clogged with air stones? You may have to reduce the length of the tubing connecting the air stone to your bullseye to make it hang straighter. – 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 would you recommend?

Sponge filters can be used as a basic piece of equipment. There aren’t many differences between brands. After using hundreds of sponge filters for a decade, we decided to make our own. We made the lift tube and base in a green color so that it blends in with plants and can hide green algae growth. However, the foam sponge is dark to conceal fish waste and other detritus.

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 surface area is ideal for shrimp and fish to graze on 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 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. To increase the filtration capacity, remove the lift tube. These sponges can be customized in multiple configurations, since three of the sponge sizes (all except for the nano sponge) can be mix and matched together. Stacking multiple sponges, rather than running them separately, has the advantage that they can be run off one air pump line. Then, if you ever need to set up a hospital tank, simply remove one sponge from the stack and it’s already seeded with beneficial bacteria to help the 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. Your sponge filter should be cleaned once a month. If bubbles are starting to fall, it is likely that the foam has become clogged with debris.

1. Disconnect the bullseye (or the entire top of the sponge filter) from the strainer. This will allow you to easily remove the foam portion 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. Reassemble the sponge filter and put it back in the tank. 5. If you find a lot of particles in your water, wait about an hour for the sponge filter.

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!