How long does aquarium filter media last?
Reusable filter media – such as the coarse sponge pad, bio rings, and Purigen – can last for many years, as long as it can be cleaned sufficiently so that its functionality is not impaired. Fine poly pads should be disposed when they turn brown in color and water cannot move through them as easily. The only way to tell if chemical filtration like activated carbon, ammonia media pads, and phosphate pads are spent is to measure the water. If you have tannins or odd odors in the water and the activated carbon no longer gets rid of them, it’s time to replace it. If you are measuring ammonia or excess phosphate in the water, then the chemical media pads are likely saturated and no longer functional.
For more information on filter media, read the full article here.