When I search the internet about this question there are many different opinion about the right interval to change filtration media in a regular freshwater tank.

On the packaging of different media filter, the interval to change the media seem to vary by a good amount. Of course, company producing filtration media are more interest to make profit than what is left in my pocket, so for them the more I change the media the better.

So far, I have never changed the filter media of my filter. About once a month I will take apart the filter and clean it in old water tank (from a water change). I will clean the sponge covering the intake (I got shrimp so no baby in the filter) than the different media from the filter (another sponge, a bag of small rock and the charcoal bag). To clean those parts, I rinse them gently in the water until there is not much coming out and then put everything back together.

I'm not really interested to ear about the [charcoal since after about two weeks][1] it don't really have any effects on chemicals but since I don't use any in the tank I don't need to have any filtered out.

So why should I change (or not) my filtration media?


  [1]: https://pets.stackexchange.com/a/372/5646