HelloI do not replace the cartridge with a water change. I was replacing them monthly like the package said. In either case i have take the input given and done the changes. The smell is gone and the fish look much better.
I know this means starting over with my cycle but in the long run i think it is worth it.
With the added sponge on the intake and clinoptilolite media my BB should have plenty of places to settle in long term