You do not need to replace it. As always, you should rinse the bio filter with aquarium water and reuse it until its unusable. I've been using the same aquaclear sponges for years. I just give it a good wash with tap water every few months if it gets too gross. When you medicate, take out the carbon insert, but after you are done medicating and the fish are cured, put the carbon in again, it will help take out the excess meds. Just to let you know, AC has a new insert called "bio max" which is a pouch of ceramic noodles like they use in expensive canister filters. these u can wash and resuse like the sponge and u dnt have to replace them for like 8-9 months.