Hello Chill...
Filters should be changed more often than most believe. In my tanks that have filters, I change them out every couple of weeks, so I know they're working well. I just rinse the new filter in some water change water and put it in the tank. You'll remove some of the bacteria during the process, but the bacteria will repopulate the tank in a short time, so no harm is done. Remember, smaller tanks need half the water changed a couple of times weekly, to keep the nitrogen from the dissolving fish waste out of the tank. If you're not there, gradually work up to this point.
B