Use sponge, biomax, then another biomax in your filter stack up. Never replace any until it is falling apart. Rinse it out as required to keep it from clogging. Which shouldn't be too often. I leave mine months without touching them and have great water parameters according to API master kit and my 25 years of using them. Take your extra sponge cut it to a suitable length, make a slit in one end and slide it over the pointed intake inside the tank. Clean this sponge often.. every water change if you want too. This sponge over the intake will help keep your filter nice and clean so you don't have to disturb your beneficial bacteria colony inside your filter as much. If your tank smells to the point that carbon will help, your over feeding and not doing enough or large enough water changes. This is the best way to use the aquaclear power filter.