Any kind of mechanical filter like a filter sock, filter floss or canister filters should be changed frequently. Ideally no more then three days. Michanical fIlters like fIlter socks do a great job of removing paticals the catch is if you don't change them often your going to have more nitrates and phosphates. If some one has cronic algae proplems the first question I ask is if they have a mechanical filter of any type and How often do you change.



