Biological Filter Sponge for Aquarium

Nope, it's not fancy. It relies on the uplift from the airflow of the air stone inserted into the tube. But honestly, I've never had cleaner tanks than when I used these unsightly hunks of sponge!

Basically, it's the surface area that promotes the growth of beneficial bacteria. So even when you clean it, you don't want to be too aggressive. You can use a standard filter to take out a lot of the 'gunk', but this little sponge will make for a much healthier aquatic environment.