Sponge Filter Not Cleaning? Here’s Why! + Fix

Last Updated on February 24, 2022 by cmoarz

Nothing is more frustrating than upgrading to a sponge filter only to find it’s not doing a very good job with the cleaning. There are actually several reasons for that which are all solvable! So if your sponge filter not cleaning properly, Here is what you need to do.

Your sponge filter is dirty

This is the most common reason for a sponge filter not cleaning efficiently. That’s why I’m going to talk about it first.

It’s actually pretty hard to tell when a sponge filter is dirty or not because from an outside appearance they look about the same clean as they do dirty.

A good rule of thumb is to clean a sponge filter at least every two months for minimal efficiency, and every 2 weeks for best performance.

To clean a sponge filter, you will need to take it out of the aquarium and place it in a bucket or bag with dirty water change water from the aquarium (never tap water).

Give it a few squeezes and repeat until the water runs clear.

Once the sponge filter is clean again, it should start functioning as it should, Unless…

It’s too small for the aquarium size you have

Just like anything else, sponge filters come in a wide variety of sizes. So if you have a small aquarium, you will need to use a small sponge filter. And if you have a large aquarium, you will need to use a large sponge filter.

If a filter is too small for the aquarium size, it will not be able to clean the water as efficiently as it should.

In order to remedy this, you can either get a bigger sponge filter or divide the aquarium into two sections with two filters- one for each side.

But size isn’t everything – And even if you have the right size filter for your tank, You might not have enough air pressure.

Air pressure is too low

Air pumps are a big part of how sponge filters operate. They push air into the filter which floats back up to the surface and starts the suction process.

If the air pressure is too low, the filter will not be able to operate efficiently.

There are a lot of different models of air pumps with varying levels of strength. High ends pumps also come with regulators to help control the air pressure.

If your air pressure is too low, you might need to invest in a better air pump or regulator.

But air pressure only works efficiently when your lift tube is long enough and submerged underwater.

Your lift tube is removed, too short, or isn’t submerged properly

The lift tube is an important part of the sponge filter because it is what helps build up suction pressure as the air bubbles rise to the surface.

I know for a fact a lot of people remove the tube because it’s unsightly and hard to hide behind plants and decorations.

But if you remove the lift tube, your sponge filter will not operate efficiently at all.

In order to fix this, you need to make sure the lift tube is long enough to create a good bit of suction, so the sponge can suck up all that dirty crud laying around.

The top of the pipe should also always be submerged completely underwater or else the suction will not be as strong.

Not having your sponge in the right spot of your aquarium

Positioning a sponge so that it’s not in the way but also effective can be a little tricky.

The best placement is always going to be different depending on what you have in your tank and the water currents (if there are any).

The sweet zone for a sponge filter is going to be where the current eventually lands and settles out random debris from the water column. Usually, this is in one of the corners of the aquarium.

But if you have a lot of decoration and plants, the sponge filter might not be able to fit in the sweet spot and will need to be placed somewhere else. Especially if they are changing the current in the tank.

If the sponge filter is not in the right spot, it will not be able to clean the water as efficiently as it should.

To find the sweet spot in your tank with a bit of experimentation so it can maximize surface area pulling power.

Last but not least, You’re expecting too much!

Sponge filters are great efficient cleaners when they are set up optimally and are working correctly.

But they will never be able to completely rid your tank of all the dirt and detritus.

Remember, they are just a part of the overall filtration process and should not be relied on 100%.

The sponge filter does a great job at getting out floating debris and clarifying water, But it doesn’t stand a chance of cleaning the gravel or big chunks of waste.

You still need to do manual vacuuming of the gravel from time to time to get the really nasty stuff.


Owner of AquariumGravel.com and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!