The filter plays a central role in cycling -- it's where most of your good bacteria live. So yes, DON"T change your filter every month. Slit open the cartridge and empty out the carbon if you can (it's a silly nuisance). Every two weeks or one month, swish the filter cartrdige around in used tank water (not tap water, the chlorine will kill your bacteria). I drain my tank into a bucket and swish my cartridges around in that, to get the worst gunk off. Then re-use the old cartridge....